RNA recognition motif (RRM) superfamily; RRM, also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain), is a highly abundant domain in eukaryotes found in proteins involved in post-transcriptional gene expression processes including mRNA and rRNA processing, RNA export, and RNA stability. This domain is 90 amino acids in length and consists of a four-stranded beta-sheet packed against two alpha-helices. RRM usually interacts with ssRNA, but is also known to interact with ssDNA as well as proteins. RRM binds a variable number of nucleotides, ranging from two to eight. The active site includes three aromatic side-chains located within the conserved RNP1 and RNP2 motifs of the domain. The RRM domain is found in a variety heterogeneous nuclear ribonucleoproteins (hnRNPs), proteins implicated in regulation of alternative splicing, and protein components of small nuclear ribonucleoproteins (snRNPs).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006 138 EKRQLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKPPGPKGKEVVALVNYTSHYAASMAKKVLVEAFRNRYGISITVRW 217
Cdd:cd12493    1 EKCELSVDGLPVSMDESKLLMVLQMLTDGVESVLLHPSPPKGKEVLAVVKYSSHRAAAMAKKALVEGSRNLCGEQVTVRW 80

                 ...
gi 182889006 218 TSF 220
Cdd:cd12493   81 LKP 83

RNA recognition motif 2 (RRM2) found in vertebrate dead end protein homolog 1 (DND1); This subgroup corresponds to the RRM2 of DND1, also termed RNA-binding motif, single-stranded-interacting protein 4. It is an RNA-binding protein that is essential for maintaining viable germ cells in vertebrates. It interacts with the 3'-untranslated region (3'-UTR) of multiple messenger RNAs (mRNAs) and prevents micro-RNA (miRNA) mediated repression of mRNA. For instance, DND1 binds cell cycle inhibitor, P27 (p27Kip1, CDKN1B), and cell cycle regulator and tumor suppressor, LATS2 (large tumor suppressor, homolog 2 of Drosophila). It helps maintain their protein expression through blocking the inhibitory function of microRNAs (miRNA) from these transcripts. DND1 may also impose another level of translational regulation to modulate expression of critical factors in embryonic stem (ES) cells. Moreover, DND1 interacts specifically with apolipoprotein B editing complex 3 (APOBEC3), a multi-functional protein inhibiting retroviral replication. The DND1-APOBEC3 interaction may play a role in maintaining viability of germ cells and for preventing germ cell tumor development. DND1 contains two conserved RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006 138 EKRQLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKPPGPKGKEVVALVNYTSHYAASMAKKVLVEAFRNRYGISITVRW 217
Cdd:cd12493    1 EKCELSVDGLPVSMDESKLLMVLQMLTDGVESVLLHPSPPKGKEVLAVVKYSSHRAAAMAKKALVEGSRNLCGEQVTVRW 80

                 ...
gi 182889006 218 TSF 220
Cdd:cd12493   81 LKP 83

heterogeneous nuclear ribonucleoprotein R, Q family; Sequences in this subfamily include the human heterogeneous nuclear ribonucleoproteins (hnRNP) R, Q, and APOBEC-1 complementation factor (aka APOBEC-1 stimulating protein). These proteins contain three RNA recognition domains (rrm: pfam00076) and a somewhat variable C-terminal domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006   17 NPQKLKSLqewMQRNSITLTQVNGQRKYGGPPPGWQGPAPGSGCEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFS 96
Cdd:TIGR01648  19 DEAALKAL---LERTGYTLVQENGQRKYGGPPPGWSGVQPGRGCEVFVGKIPRDLYEDELVPLFEKAGPIYELRLMMDFS 95

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006   97 GQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTVRRSTEKRQLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKP-P 175
Cdd:TIGR01648  96 GQNRGYAFVTFCGKEEAKEAVKLLNNYEIRPGRLLGVCISVDNCRLFVGGIPKNKKREEILEEFSKVTEGVVDVIVYHsA 175

                         170       180       190       200
                  ....*....|....*....|....*....|....*....|...
gi 182889006  176 GPKGKEV-VALVNYTSHYAASMAKKVLVEAFRNRYGISITVRW 217
Cdd:TIGR01648 176 ADKKKNRgFAFVEYESHRAAAMARRKLMPGRIQLWGHVIAVDW 218

RNA recognition motif;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 182889006    62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRLpEGGCLTV 133
Cdd:smart00360   2 LFVGNLPPDTTEEELRELFSKFGKVESVRLVRDkETGKSKGFAFVEFESEEDAEKALEALNGKEL-DGRPLKV 73

RNA recognition motif 2 (RRM2) found in vertebrate dead end protein homolog 1 (DND1); This subgroup corresponds to the RRM2 of DND1, also termed RNA-binding motif, single-stranded-interacting protein 4. It is an RNA-binding protein that is essential for maintaining viable germ cells in vertebrates. It interacts with the 3'-untranslated region (3'-UTR) of multiple messenger RNAs (mRNAs) and prevents micro-RNA (miRNA) mediated repression of mRNA. For instance, DND1 binds cell cycle inhibitor, P27 (p27Kip1, CDKN1B), and cell cycle regulator and tumor suppressor, LATS2 (large tumor suppressor, homolog 2 of Drosophila). It helps maintain their protein expression through blocking the inhibitory function of microRNAs (miRNA) from these transcripts. DND1 may also impose another level of translational regulation to modulate expression of critical factors in embryonic stem (ES) cells. Moreover, DND1 interacts specifically with apolipoprotein B editing complex 3 (APOBEC3), a multi-functional protein inhibiting retroviral replication. The DND1-APOBEC3 interaction may play a role in maintaining viability of germ cells and for preventing germ cell tumor development. DND1 contains two conserved RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006 138 EKRQLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKPPGPKGKEVVALVNYTSHYAASMAKKVLVEAFRNRYGISITVRW 217
Cdd:cd12493    1 EKCELSVDGLPVSMDESKLLMVLQMLTDGVESVLLHPSPPKGKEVLAVVKYSSHRAAAMAKKALVEGSRNLCGEQVTVRW 80

                 ...
gi 182889006 218 TSF 220
Cdd:cd12493   81 LKP 83

heterogeneous nuclear ribonucleoprotein R, Q family; Sequences in this subfamily include the human heterogeneous nuclear ribonucleoproteins (hnRNP) R, Q, and APOBEC-1 complementation factor (aka APOBEC-1 stimulating protein). These proteins contain three RNA recognition domains (rrm: pfam00076) and a somewhat variable C-terminal domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006   17 NPQKLKSLqewMQRNSITLTQVNGQRKYGGPPPGWQGPAPGSGCEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFS 96
Cdd:TIGR01648  19 DEAALKAL---LERTGYTLVQENGQRKYGGPPPGWSGVQPGRGCEVFVGKIPRDLYEDELVPLFEKAGPIYELRLMMDFS 95

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006   97 GQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTVRRSTEKRQLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKP-P 175
Cdd:TIGR01648  96 GQNRGYAFVTFCGKEEAKEAVKLLNNYEIRPGRLLGVCISVDNCRLFVGGIPKNKKREEILEEFSKVTEGVVDVIVYHsA 175

                         170       180       190       200
                  ....*....|....*....|....*....|....*....|...
gi 182889006  176 GPKGKEV-VALVNYTSHYAASMAKKVLVEAFRNRYGISITVRW 217
Cdd:TIGR01648 176 ADKKKNRgFAFVEYESHRAAAMARRKLMPGRIQLWGHVIAVDW 218

RNA recognition motif 1 (RRM1) found in heterogeneous nuclear ribonucleoprotein R (hnRNP R) and similar proteins; This subfamily corresponds to the RRM1 in hnRNP R, hnRNP Q, APOBEC-1 complementation factor (ACF), and dead end protein homolog 1 (DND1). hnRNP R is a ubiquitously expressed nuclear RNA-binding protein that specifically binds mRNAs with a preference for poly(U) stretches. It has been implicated in mRNA processing and mRNA transport, and also acts as a regulator to modify binding to ribosomes and RNA translation. hnRNP Q is also a ubiquitously expressed nuclear RNA-binding protein. It has been identified as a component of the spliceosome complex, as well as a component of the apobec-1 editosome, and has been implicated in the regulation of specific mRNA transport. ACF is an RNA-binding subunit of a core complex that interacts with apoB mRNA to facilitate C to U RNA editing. It may also act as an apoB mRNA recognition factor and chaperone, and play a key role in cell growth and differentiation. DND1 is essential for maintaining viable germ cells in vertebrates. It interacts with the 3'-untranslated region (3'-UTR) of multiple messenger RNAs (mRNAs) and prevents micro-RNA (miRNA) mediated repression of mRNA. This family also includes two functionally unknown RNA-binding proteins, RBM46 and RBM47. All members in this family, except for DND1, contain three conserved RNA recognition motifs (RRMs); DND1 harbors only two RRMs.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 182889006  59 GCEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTVRRS 136
Cdd:cd12249    1 GCEVFVGKIPRDVFEDELVPLFEKCGKIYELRLMMDFSGLNRGYAFVTYTNKEAAQRAVKTLNNYEIRPGKLLGVCIS 78

RNA recognition motif 1 (RRM1) found in vertebrate RNA-binding protein 47 (RBM47); This subgroup corresponds to the RRM1 of RBM47, a putative RNA-binding protein that shows high sequence homology with heterogeneous nuclear ribonucleoprotein R (hnRNP R) and heterogeneous nuclear ribonucleoprotein Q (hnRNP Q). Its biological function remains unclear. Like hnRNP R and hnRNP Q, RBM47 contains two well-defined and one degenerated RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 182889006  59 GCEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTV 133
Cdd:cd12485    1 GCEVFVGKIPRDVYEDELVPVFESVGRIYEMRLMMDFDGKNRGYAFVMYTQKHEAKRAVRELNNYEIRPGRLLGV 75

RNA recognition motif 1 (RRM1) found in vertebrate heterogeneous nuclear ribonucleoprotein R (hnRNP R); This subgroup corresponds to the RRM1 of hnRNP R, which is a ubiquitously expressed nuclear RNA-binding protein that specifically binds mRNAs with a preference for poly(U) stretches. Upon binding of RNA, hnRNP R forms oligomers, most probably dimers. hnRNP R has been implicated in mRNA processing and mRNA transport, and also acts as a regulator to modify binding to ribosomes and RNA translation. It is predominantly located in axons of motor neurons and to a much lower degree in sensory axons. In axons of motor neurons, it also functions as a cytosolic protein and interacts with wild type of survival motor neuron (SMN) proteins directly, further providing a molecular link between SMN and the spliceosome. Moreover, hnRNP R plays an important role in neural differentiation and development, and in retinal development and light-elicited cellular activities. hnRNP R contains an acidic auxiliary N-terminal region, followed by two well defined and one degenerated RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), and a C-terminal RGG motif; it binds RNA through its RRM domains.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 182889006  59 GCEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTV 133
Cdd:cd12482    1 GTEVFVGKIPRDLYEDELVPLFEKAGPIWDLRLMMDpLSGQNRGYAFITFCNKEAAQEAVKLCDNYEIRPGKHLGV 76

RNA recognition motif (RRM) superfamily; RRM, also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain), is a highly abundant domain in eukaryotes found in proteins involved in post-transcriptional gene expression processes including mRNA and rRNA processing, RNA export, and RNA stability. This domain is 90 amino acids in length and consists of a four-stranded beta-sheet packed against two alpha-helices. RRM usually interacts with ssRNA, but is also known to interact with ssDNA as well as proteins. RRM binds a variable number of nucleotides, ranging from two to eight. The active site includes three aromatic side-chains located within the conserved RNP1 and RNP2 motifs of the domain. The RRM domain is found in a variety heterogeneous nuclear ribonucleoproteins (hnRNPs), proteins implicated in regulation of alternative splicing, and protein components of small nuclear ribonucleoproteins (snRNPs).

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRLpEGGCLTVR 134
Cdd:cd00590    1 LFVGNLPPDTTEEDLRELFSKFGEVVSVRIVRDRDGKSKGFAFVEFESPEDAEKALEALNGTEL-GGRPLKVS 72

RNA recognition motif (RRM) found in cleavage stimulation factor subunit 2 (CSTF2), yeast ortholog mRNA 3'-end-processing protein RNA15 and similar proteins; This subfamily corresponds to the RRM domain of CSTF2, its tau variant and eukaryotic homologs. CSTF2, also termed cleavage stimulation factor 64 kDa subunit (CstF64), is the vertebrate conterpart of yeast mRNA 3'-end-processing protein RNA15. It is expressed in all somatic tissues and is one of three cleavage stimulatory factor (CstF) subunits required for polyadenylation. CstF64 contains an N-terminal RNA recognition motif (RRM), also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain), a CstF77-binding domain, a repeated MEARA helical region and a conserved C-terminal domain reported to bind the transcription factor PC-4. During polyadenylation, CstF interacts with the pre-mRNA through the RRM of CstF64 at U- or GU-rich sequences within 10 to 30 nucleotides downstream of the cleavage site. CSTF2T, also termed tauCstF64, is a paralog of the X-linked cleavage stimulation factor CstF64 protein that supports polyadenylation in most somatic cells. It is expressed during meiosis and subsequent haploid differentiation in a more limited set of tissues and cell types, largely in meiotic and postmeiotic male germ cells, and to a lesser extent in brain. The loss of CSTF2T will cause male infertility, as it is necessary for spermatogenesis and fertilization. Moreover, CSTF2T is required for expression of genes involved in morphological differentiation of spermatids, as well as for genes having products that function during interaction of motile spermatozoa with eggs. It promotes germ cell-specific patterns of polyadenylation by using its RRM to bind to different sequence elements downstream of polyadenylation sites than does CstF64. The family also includes yeast ortholog mRNA 3'-end-processing protein RNA15 and similar proteins. RNA15 is a core subunit of cleavage factor IA (CFIA), an essential transcriptional 3'-end processing factor from Saccharomyces cerevisiae. RNA recognition by CFIA is mediated by an N-terminal RRM, which is contained in the RNA15 subunit of the complex. The RRM of RNA15 has a strong preference for GU-rich RNAs, mediated by a binding pocket that is entirely conserved in both yeast and vertebrate RNA15 orthologs.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMM-NFSGQTRGFAYAKYGDPLTASAAVTTLHQYRL 125
Cdd:cd12398    3 VFVGNIPYDATEEQLKEIFSEVGPVVSFRLVTdRETGKPKGYGFCEFRDAETALSAVRNLNGYEL 67

RNA recognition motif 1 (RRM1) found in squamous cell carcinoma antigen recognized by T-cells 3 (SART3) and similar proteins; This subfamily corresponds to the RRM1 of SART3, also termed Tat-interacting protein of 110 kDa (Tip110), an RNA-binding protein expressed in the nucleus of the majority of proliferating cells, including normal cells and malignant cells, but not in normal tissues except for the testes and fetal liver. It is involved in the regulation of mRNA splicing probably via its complex formation with RNA-binding protein with a serine-rich domain (RNPS1), a pre-mRNA-splicing factor. SART3 has also been identified as a nuclear Tat-interacting protein that regulates Tat transactivation activity through direct interaction and functions as an important cellular factor for HIV-1 gene expression and viral replication. In addition, SART3 is required for U6 snRNP targeting to Cajal bodies. It binds specifically and directly to the U6 snRNA, interacts transiently with the U6 and U4/U6 snRNPs, and promotes the reassembly of U4/U6 snRNPs after splicing in vitro. SART3 contains an N-terminal half-a-tetratricopeptide repeat (HAT)-rich domain, a nuclearlocalization signal (NLS) domain, and two C-terminal RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAA 116
Cdd:cd12391    2 VFVSNLDYSVPEDKIREIFSGCGEITDVRLVKNYKGKSKGYCYVEFKDEESAQKA 56

RNA recognition motif 2 (RRM2) found in squamous cell carcinoma antigen recognized by T-cells 3 (SART3) and similar proteins; This subfamily corresponds to the RRM2 of SART3, also termed Tat-interacting protein of 110 kDa (Tip110), is an RNA-binding protein expressed in the nucleus of the majority of proliferating cells, including normal cells and malignant cells, but not in normal tissues except for the testes and fetal liver. It is involved in the regulation of mRNA splicing probably via its complex formation with RNA-binding protein with a serine-rich domain (RNPS1), a pre-mRNA-splicing factor. SART3 has also been identified as a nuclear Tat-interacting protein that regulates Tat transactivation activity through direct interaction and functions as an important cellular factor for HIV-1 gene expression and viral replication. In addition, SART3 is required for U6 snRNP targeting to Cajal bodies. It binds specifically and directly to the U6 snRNA, interacts transiently with the U6 and U4/U6 snRNPs, and promotes the reassembly of U4/U6 snRNPs after splicing in vitro. SART3 contains an N-terminal half-a-tetratricopeptide repeat (HAT)-rich domain, a nuclearlocalization signal (NLS) domain, and two C-terminal RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*.
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAV 117
Cdd:cd12392    5 LFVKGLPFSCTKEELEELFKQHGTVKDVRLVTYRNGKPKGLAYVEYENEADASQAV 60

RNA recognition motif 3 (RRM3) found in CELF/Bruno-like family of RNA binding proteins CELF1, CELF2, CELF3, CELF4, CELF5, CELF6 and similar proteins; This subgroup corresponds to the RRM3 of the CUGBP1 and ETR-3-like factors (CELF) or BRUNOL (Bruno-like) proteins, a family of structurally related RNA-binding proteins involved in the regulation of pre-mRNA splicing in the nucleus and in the control of mRNA translation and deadenylation in the cytoplasm. The family contains six members: CELF-1 (also termed BRUNOL-2, or CUG-BP1, or NAPOR, or EDEN-BP), CELF-2 (also termed BRUNOL-3, or ETR-3, or CUG-BP2, or NAPOR-2), CELF-3 (also termed BRUNOL-1, or TNRC4, or ETR-1, or CAGH4, or ER DA4), CELF-4 (also termed BRUNOL-4), CELF-5 (also termed BRUNOL-5), CELF-6 (also termed BRUNOL-6). They all contain three highly conserved RNA recognition motifs (RRMs), also known as RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains): two consecutive RRMs (RRM1 and RRM2) situated in the N-terminal region followed by a linker region and the third RRM (RRM3) close to the C-terminus of the protein. The low sequence conservation of the linker region is highly suggestive of a large variety in the co-factors that associate with the various CELF family members. Based on both sequence similarity and function, the CELF family can be divided into two subfamilies, the first containing CELFs 1 and 2, and the second containing CELFs 3, 4, 5, and 6. The different CELF proteins may act through different sites on at least some substrates. Furthermore, CELF proteins may interact with each other in varying combinations to influence alternative splicing in different contexts.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQY 123
Cdd:cd12362    1 LFVYHLPNEFTDQDLYQLFAPFGNVVSAKVFVDkNTGRSKGFGFVSYDNPLSAQAAIKAMNGF 63

RNA recognition motif (RRM) found in cleavage stimulation factor subunit 2 (CSTF2), cleavage stimulation factor subunit 2 tau variant (CSTF2T) and similar proteins; This subgroup corresponds to the RRM domain of CSTF2, its tau variant and eukaryotic homologs. CSTF2, also termed cleavage stimulation factor 64 kDa subunit (CstF64), is the vertebrate conterpart of yeast mRNA 3'-end-processing protein RNA15. It is expressed in all somatic tissues and is one of three cleavage stimulatory factor (CstF) subunits required for polyadenylation. CstF64 contains an N-terminal RNA recognition motif (RRM), also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain), a CstF77-binding domain, a repeated MEARA helical region and a conserved C-terminal domain reported to bind the transcription factor PC-4. During polyadenylation, CstF interacts with the pre-mRNA through the RRM of CstF64 at U- or GU-rich sequences within 10 to 30 nucleotides downstream of the cleavage site. CSTF2T, also termed tauCstF64, is a paralog of the X-linked cleavage stimulation factor CstF64 protein that supports polyadenylation in most somatic cells. It is expressed during meiosis and subsequent haploid differentiation in a more limited set of tissues and cell types, largely in meiotic and postmeiotic male germ cells, and to a lesser extent in brain. The loss of CSTF2T will cause male infertility, as it is necessary for spermatogenesis and fertilization. Moreover, CSTF2T is required for expression of genes involved in morphological differentiation of spermatids, as well as for genes having products that function during interaction of motile spermatozoa with eggs. It promotes germ cell-specific patterns of polyadenylation by using its RRM to bind to different sequence elements downstream of polyadenylation sites than does CstF64.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNF-SGQTRGFAYAKYGDPLTASAAVTTLHQYRL 125
Cdd:cd12671    9 VFVGNIPYEATEEQLKDIFSEVGPVVSFRLVYDReTGKPKGYGFCEYQDQETALSAMRNLNGYEL 73

RNA recognition motif 3 (RRM3) found found in type I polyadenylate-binding proteins; This subfamily corresponds to the RRM3 of type I poly(A)-binding proteins (PABPs), highly conserved proteins that bind to the poly(A) tail present at the 3' ends of most eukaryotic mRNAs. They have been implicated in the regulation of poly(A) tail length during the polyadenylation reaction, translation initiation, mRNA stabilization by influencing the rate of deadenylation and inhibition of mRNA decapping. The family represents type I polyadenylate-binding proteins (PABPs), including polyadenylate-binding protein 1 (PABP-1 or PABPC1), polyadenylate-binding protein 3 (PABP-3 or PABPC3), polyadenylate-binding protein 4 (PABP-4 or APP-1 or iPABP), polyadenylate-binding protein 5 (PABP-5 or PABPC5), polyadenylate-binding protein 1-like (PABP-1-like or PABPC1L), polyadenylate-binding protein 1-like 2 (PABPC1L2 or RBM32), polyadenylate-binding protein 4-like (PABP-4-like or PABPC4L), yeast polyadenylate-binding protein, cytoplasmic and nuclear (PABP or ACBP-67), and similar proteins. PABP-1 is an ubiquitously expressed multifunctional protein that may play a role in 3' end formation of mRNA, translation initiation, mRNA stabilization, protection of poly(A) from nuclease activity, mRNA deadenylation, inhibition of mRNA decapping, and mRNP maturation. Although PABP-1 is thought to be a cytoplasmic protein, it is also found in the nucleus. PABP-1 may be involved in nucleocytoplasmic trafficking and utilization of mRNP particles. PABP-1 contains four copies of RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), a less well conserved linker region, and a proline-rich C-terminal conserved domain (CTD). PABP-3 is a testis-specific poly(A)-binding protein specifically expressed in round spermatids. It is mainly found in mammalian and may play an important role in the testis-specific regulation of mRNA homeostasis. PABP-3 shows significant sequence similarity to PABP-1. However, it binds to poly(A) with a lower affinity than PABP-1. PABP-1 possesses an A-rich sequence in its 5'-UTR and allows binding of PABP and blockage of translation of its own mRNA. In contrast, PABP-3 lacks the A-rich sequence in its 5'-UTR. PABP-4 is an inducible poly(A)-binding protein (iPABP) that is primarily localized to the cytoplasm. It shows significant sequence similarity to PABP-1 as well. The RNA binding properties of PABP-1 and PABP-4 appear to be identical. PABP-5 is encoded by PABPC5 gene within the X-specific subinterval, and expressed in fetal brain and in a range of adult tissues in mammalian, such as ovary and testis. It may play an important role in germ cell development. Moreover, unlike other PABPs, PABP-5 contains only four RRMs, but lacks both the linker region and the CTD. PABP-1-like and PABP-1-like 2 are the orthologs of PABP-1. PABP-4-like is the ortholog of PABP-5. Their cellular functions remain unclear. The family also includes the yeast PABP, a conserved poly(A) binding protein containing poly(A) tails that can be attached to the 3'-ends of mRNAs. The yeast PABP and its homologs may play important roles in the initiation of translation and in mRNA decay. Like vertebrate PABP-1, the yeast PABP contains four RRMs, a linker region, and a proline-rich CTD as well. The first two RRMs are mainly responsible for specific binding to poly(A). The proline-rich region may be involved in protein-protein interactions.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLH 121
Cdd:cd12380    4 VYVKNFGEDVDDDELKELFEKYGKITSAKVMKDDSGKSKGFGFVNFENHEAAQKAVEELN 63

RNA recognition motif 1 (RRM1) found in vertebrate Hu-antigen B (HuB); This subgroup corresponds to the RRM1 of HuB, also termed ELAV-like protein 2 (ELAV-2), or ELAV-like neuronal protein 1, or nervous system-specific RNA-binding protein Hel-N1 (Hel-N1), one of the neuronal members of the Hu family. The neuronal Hu proteins play important roles in neuronal differentiation, plasticity and memory. HuB is also expressed in gonads and is up-regulated during neuronal differentiation of embryonic carcinoma P19 cells. Like other Hu proteins, HuB contains three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). RRM1 and RRM2 may cooperate in binding to an AU-rich RNA element (ARE). RRM3 may help to maintain the stability of the RNA-protein complex, and might also bind to poly(A) tails or be involved in protein-protein interactions.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 182889006  58 SGCEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRL 125
Cdd:cd12771    3 SKTNLIVNYLPQNMTQEELKSLFGSIGEIESCKLVRDkITGQSLGYGFVNYIEPKDAEKAINTLNGLRL 71

RNA recognition motif 2 (RRM2) found in U2 large nuclear ribonucleoprotein auxiliary factor U2AF 65 kDa subunit (U2AF65) and similar proteins; This subfamily corresponds to the RRM2 of U2AF65 and dU2AF50. U2AF65, also termed U2AF2, is the large subunit of U2 small nuclear ribonucleoprotein (snRNP) auxiliary factor (U2AF), which has been implicated in the recruitment of U2 snRNP to pre-mRNAs and is a highly conserved heterodimer composed of large and small subunits. U2AF65 specifically recognizes the intron polypyrimidine tract upstream of the 3' splice site and promotes binding of U2 snRNP to the pre-mRNA branchpoint. U2AF65 also plays an important role in the nuclear export of mRNA. It facilitates the formation of a messenger ribonucleoprotein export complex, containing both the NXF1 receptor and the RNA substrate. Moreover, U2AF65 interacts directly and specifically with expanded CAG RNA, and serves as an adaptor to link expanded CAG RNA to NXF1 for RNA export. U2AF65 contains an N-terminal RS domain rich in arginine and serine, followed by a proline-rich segment and three C-terminal RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). The N-terminal RS domain stabilizes the interaction of U2 snRNP with the branch point (BP) by contacting the branch region, and further promotes base pair interactions between U2 snRNA and the BP. The proline-rich segment mediates protein-protein interactions with the RRM domain of the small U2AF subunit (U2AF35 or U2AF1). The RRM1 and RRM2 are sufficient for specific RNA binding, while RRM3 is responsible for protein-protein interactions. The family also includes Splicing factor U2AF 50 kDa subunit (dU2AF50), the Drosophila ortholog of U2AF65. dU2AF50 functions as an essential pre-mRNA splicing factor in flies. It associates with intronless mRNAs and plays a significant and unexpected role in the nuclear export of a large number of intronless mRNAs.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRLpEGGCLTVRR 135
Cdd:cd12231    3 LFIGGLPNYLNEDQVKELLQSFGKLKAFNLVKDsATGLSKGYAFCEYVDDNVTDQAIAGLNGMQL-GDKKLLVQR 76

RNA recognition motif 2 (RRM2) found in Nicotiana sylvestris chloroplastic 33 kDa ribonucleoprotein (NsCP33) and similar proteins; The family includes NsCP33, Arabidopsis thaliana chloroplastic 31 kDa ribonucleoprotein (CP31A) and mitochondrial glycine-rich RNA-binding protein 2 (AtGR-RBP2). NsCP33 may be involved in splicing and/or processing of chloroplast RNA's. AtCP31A, also called RNA-binding protein 1/2/3 (AtRBP33), or RNA-binding protein CP31A, or RNA-binding protein RNP-T, or RNA-binding protein cp31, is required for specific RNA editing events in chloroplasts and stabilizes specific chloroplast mRNAs, as well as for normal chloroplast development under cold stress conditions by stabilizing transcripts of numerous mRNAs under these conditions. CP31A may modulate telomere replication through RNA binding domains. AtGR-RBP2, also called AtRBG2, or glycine-rich protein 2 (AtGRP2), or mitochondrial RNA-binding protein 1a (At-mRBP1a), plays a role in RNA transcription or processing during stress. It binds RNAs and DNAs sequence with a preference to single-stranded nucleic acids. AtGR-RBP2 displays strong affinity to poly(U) sequence. It exerts cold and freezing tolerance, probably by exhibiting an RNA chaperone activity during the cold and freezing adaptation process. Some members in this family contain two RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). The model corresponds to the second RRM motif.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRLpEGGCLTVR 134
Cdd:cd21608    2 LYVGNLSWDTTEDDLRDLFSEFGEVESAKVITDrETGRSRGFGFVTFSTAEAAEAAIDALNGKEL-DGRSIVVN 74

RNA recognition motif 2 (RRM2) found in vertebrate RNA-binding protein 46 (RBM46); This subgroup corresponds to the RRM2 of RBM46, also termed cancer/testis antigen 68 (CT68). It is a putative RNA-binding protein that shows high sequence homology with heterogeneous nuclear ribonucleoprotein R (hnRNP R) and heterogeneous nuclear ribonucleoprotein Q (hnRNP Q). Its biological function remains unclear. Like hnRNP R and hnRNP Q, RBM46 contains two well-defined and one degenerated RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006 141 QLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKPPGP-KGKEV-VALVNYTSHYAASMAKKVLVEAFRNRYGISITVRWT 218
Cdd:cd12492    4 RLFIGAIPKEKKKEEILEEMKKVTEGVVDVIVYPSATdKTKNRgFAFVEYESHRAAAMARRKLIPGTFQLWGHTIQVDWA 83

                 .
gi 182889006 219 S 219
Cdd:cd12492   84 D 84

RNA recognition motif 2 (RRM2) found in vertebrate APOBEC-1 complementation factor (ACF); This subgroup corresponds to the RRM2 of ACF, also termed APOBEC-1-stimulating protein, an RNA-binding subunit of a core complex that interacts with apoB mRNA to facilitate C to U RNA editing. It may also act as an apoB mRNA recognition factor and chaperone and play a key role in cell growth and differentiation. ACF shuttles between the cytoplasm and nucleus. ACF contains three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), which display high affinity for an 11 nucleotide AU-rich mooring sequence 3' of the edited cytidine in apoB mRNA. All three RRMs may be required for complementation of editing activity in living cells. RRM2/3 are implicated in ACF interaction with APOBEC-1.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 182889006 141 QLRLGDLPVSMNESKLLMVLQMLSDGVEDVLLKPPGP-KGKEV-VALVNYTSHYAASMAKKVLVEAFRNRYGISITVRW 217
Cdd:cd12490    5 RLFVGGIPKTKKREEILAEMKKVTDGVVDVIVYPSAAdKTKNRgFAFVEYESHRAAAMARRKLLPGRIQLWGHPIAVDW 83

RNA recognition motif 2 (RRM2) found in granule-associated RNA binding proteins (p40-TIA-1 and TIAR), and yeast nuclear and cytoplasmic polyadenylated RNA-binding protein PUB1; This subfamily corresponds to the RRM3 of TIA-1, TIAR, and PUB1. Nucleolysin TIA-1 isoform p40 (p40-TIA-1 or TIA-1) and nucleolysin TIA-1-related protein (TIAR) are granule-associated RNA binding proteins involved in inducing apoptosis in cytotoxic lymphocyte (CTL) target cells. They share high sequence similarity and are expressed in a wide variety of cell types. TIA-1 can be phosphorylated by a serine/threonine kinase that is activated during Fas-mediated apoptosis.TIAR is mainly localized in the nucleus of hematopoietic and nonhematopoietic cells. It is translocated from the nucleus to the cytoplasm in response to exogenous triggers of apoptosis. Both TIA-1 and TIAR bind specifically to poly(A) but not to poly(C) homopolymers. They are composed of three N-terminal highly homologous RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), and a glutamine-rich C-terminal auxiliary domain containing a lysosome-targeting motif. TIA-1 and TIAR interact with RNAs containing short stretches of uridylates and their RRM2 can mediate the specific binding to uridylate-rich RNAs. The C-terminal auxiliary domain may be responsible for interacting with other proteins. In addition, TIA-1 and TIAR share a potential serine protease-cleavage site (Phe-Val-Arg) localized at the junction between their RNA binding domains and their C-terminal auxiliary domains. This subfamily also includes a yeast nuclear and cytoplasmic polyadenylated RNA-binding protein PUB1, termed ARS consensus-binding protein ACBP-60, or poly uridylate-binding protein, or poly(U)-binding protein, which has been identified as both a heterogeneous nuclear RNA-binding protein (hnRNP) and a cytoplasmic mRNA-binding protein (mRNP). It may be stably bound to a translationally inactive subpopulation of mRNAs within the cytoplasm. PUB1 is distributed in both, the nucleus and the cytoplasm, and binds to poly(A)+ RNA (mRNA or pre-mRNA). Although it is one of the major cellular proteins cross-linked by UV light to polyadenylated RNAs in vivo, PUB1 is nonessential for cell growth in yeast. PUB1 also binds to T-rich single stranded DNA (ssDNA); however, there is no strong evidence implicating PUB1 in the mechanism of DNA replication. PUB1 contains three RRMs, and a GAR motif (glycine and arginine rich stretch) that is located between RRM2 and RRM3.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 182889006  60 CEVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMmnfsgQTRGFAYAKYGDPLTASAAVTTLH 121
Cdd:cd12354    1 TTVYVGNITKGLTEALLQQTFSPFGQILEVRVF-----PDKGYAFIRFDSHEAATHAIVSVN 57

double-stranded RNA binding motif of APOBEC1 complementation factor (A1CF), RNA-binding protein 46 (RBM46) and similar proteins; The family includes two dsRNA-binding motif-containing proteins, A1CF and RBM46. A1CF (also known as APOBEC1-stimulating protein) is an essential component of the apolipoprotein B mRNA editing enzyme complex which is responsible for the posttranscriptional editing of a CAA codon for Gln to a UAA codon for stop in APOB mRNA. A1CF binds to APOB mRNA and is probably responsible for docking the catalytic subunit, APOBEC1, to the mRNA to allow it to deaminate its target cytosine. RBM46 (also called cancer/testis antigen 68 (CT68), or RNA-binding motif protein 46) plays a novel role in the regulation of embryonic stem cell (ESC) differentiation by regulating the degradation of beta-catenin mRNA. It also regulates trophectoderm specification by stabilizing Cdx2 mRNA in early mouse embryos. Members of this family contain three RNA recognition motifs (RRMs) and a C-terminal double-stranded RNA binding motif (DSRM) that is not sequence specific, but highly specific for dsRNAs of various origin and structure.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....
gi 182889006 325 AVSHLQWMCEVNRLGSPQYEVHfHHAAPDGFLYFAFKVLIPGLP 368
Cdd:cd19872    2 PVQILEEICQKNGWGEPVYQLL-STSSNNEVQLFIYKVTIPNLP 44

RNA recognition motif 2 (RRM2) found in Drosophila melanogaster Bruno protein and similar proteins; This subgroup corresponds to the RRM2 of Bruno, a Drosophila RNA recognition motif (RRM)-containing protein that plays a central role in regulation of Oskar (Osk) expression. It mediates repression by binding to regulatory Bruno response elements (BREs) in the Osk mRNA 3' UTR. The full-length Bruno protein contains three RRMs, two located in the N-terminal half of the protein and the third near the C-terminus, separated by a linker region.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 182889006  61 EVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEG 128
Cdd:cd12636    3 KLFVGMLSKKCNESDVRIMFSPYGSIEECTVLRDQNGKSRGCAFVTFTSRQCAVNAIKAMHHSQTMEG 70

RNA recognition motif 1 (RRM1) found in heterogeneous nuclear ribonucleoprotein M (hnRNP M) and similar proteins; This subfamily corresponds to the RRM1 of heterogeneous nuclear ribonucleoprotein M (hnRNP M), myelin expression factor 2 (MEF-2 or MyEF-2 or MST156) and similar proteins. hnRNP M is pre-mRNA binding protein that may play an important role in the pre-mRNA processing. It also preferentially binds to poly(G) and poly(U) RNA homopolymers. Moreover, hnRNP M is able to interact with early spliceosomes, further influencing splicing patterns of specific pre-mRNAs. hnRNP M functions as the receptor of carcinoembryonic antigen (CEA) that contains the penta-peptide sequence PELPK signaling motif. In addition, hnRNP M and another splicing factor Nova-1 work together as dopamine D2 receptor (D2R) pre-mRNA-binding proteins. They regulate alternative splicing of D2R pre-mRNA in an antagonistic manner. hnRNP M contains three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), and an unusual hexapeptide-repeat region rich in methionine and arginine residues (MR repeat motif). MEF-2 is a sequence-specific single-stranded DNA (ssDNA) binding protein that binds specifically to ssDNA derived from the proximal (MB1) element of the myelin basic protein (MBP) promoter and represses transcription of the MBP gene. MEF-2 shows high sequence homology with hnRNP M. It also contains three RRMs, which may be responsible for its ssDNA binding activity.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 182889006  62 VFISQIPNDVYEDRLIPLFQS-IGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRL 125
Cdd:cd12385    2 VFISNIPYDYKWQDLKDLFREkVGEVTYVELFKDENGKSRGCGIVEFKDLESVQKALETMNRYEL 66

RNA recognition motif 1 (RRM1) found in chloroplastic plastid-specific 30S ribosomal protein 2 (PSRP-2) and similar proteins; PSRP-2, also called chloroplastic 30S ribosomal protein 2, or chloroplastic small ribosomal subunit protein cS22, is a component of the chloroplast ribosome (chloro-ribosome), a dedicated translation machinery responsible for the synthesis of chloroplast genome-encoded proteins, including proteins of the transcription and translation machinery and components of the photosynthetic apparatus. It binds single strand DNA (ssDNA) and RNA in vitro. It exhibits RNA chaperone activity and regulates negatively resistance responses to abiotic stresses during seed germination (e.g. salt, dehydration, and low temperature) and seedling growth (e.g. salt). The family also includes Nicotiana sylvestris chloroplastic 33 kDa ribonucleoprotein (NsCP33) and Arabidopsis thaliana chloroplastic 31 kDa ribonucleoprotein (AtCP31A). NsCP33 may be involved in splicing and/or processing of chloroplast RNA's. AtCP31A, also called RNA-binding protein 1/2/3 (AtRBP33), or RNA-binding protein CP31A, or RNA-binding protein RNP-T, or RNA-binding protein cp31, is required for specific RNA editing events in chloroplasts and stabilizes specific chloroplast mRNAs, as well as for normal chloroplast development under cold stress conditions by stabilizing transcripts of numerous mRNAs under these conditions. CP31A may modulate telomere replication through RNA binding domains. Members in this family contain two RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). The model corresponds to the first RRM motif.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 182889006  61 EVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRLpEGGCLTVRRS 136
Cdd:cd21609    1 RLYVGNIPRNVTSEELAKIFEEAGTVEIAEVMYDrYTGRSRGFGFVTMGSVEDAKAAIEKLNGTEV-GGREIKVNIT 76

RNA recognition motif 1 (RRM1) found in yeast multiple RNA-binding domain-containing protein 1 (MRD1) and similar proteins; This subgroup corresponds to the RRM1 of MRD1 which is encoded by a novel yeast gene MRD1 (multiple RNA-binding domain). It is well-conserved in yeast and its homologs exist in all eukaryotes. MRD1 is present in the nucleolus and the nucleoplasm. It interacts with the 35 S precursor rRNA (pre-rRNA) and U3 small nucleolar RNAs (snoRNAs). MRD1 is essential for the initial processing at the A0-A2 cleavage sites in the 35 S pre-rRNA. It contains 5 conserved RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), which may play an important structural role in organizing specific rRNA processing events.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQ 122
Cdd:cd12565    3 IIVKNLPKYVTEKRLKEHFSKKGEITDVKVMRTKDGKSRRFGFIGFKSEEEAQKAVKYFNK 63

RNA recognition motif 2 (RRM2) found in CUGBP Elav-like family member CELF-1, CELF-2 and similar proteins; This subgroup corresponds to the RRM2 of CELF-1 (also termed BRUNOL-2, or CUG-BP1, or EDEN-BP), CELF-2 (also termed BRUNOL-3, or ETR-3, or CUG-BP2, or NAPOR), both of which belong to the CUGBP1 and ETR-3-like factors (CELF) or BRUNOL (Bruno-like) family of RNA-binding proteins that have been implicated in the regulation of pre-mRNA splicing and in the control of mRNA translation and deadenylation. CELF-1 is strongly expressed in all adult and fetal tissues tested. Human CELF-1 is a nuclear and cytoplasmic RNA-binding protein that regulates multiple aspects of nuclear and cytoplasmic mRNA processing, with implications for onset of type 1 myotonic dystrophy (DM1), a neuromuscular disease associated with an unstable CUG triplet expansion in the 3'-UTR (3'-untranslated region) of the DMPK (myotonic dystrophy protein kinase) gene; it preferentially targets UGU-rich mRNA elements. It has been shown to bind to a Bruno response element, a cis-element involved in translational control of oskar mRNA in Drosophila, and share sequence similarity to Bruno, the Drosophila protein that mediates this process. The Xenopus homolog embryo deadenylation element-binding protein (EDEN-BP) mediates sequence-specific deadenylation of Eg5 mRNA. It binds specifically to the EDEN motif in the 3'-untranslated regions of maternal mRNAs and targets these mRNAs for deadenylation and translational repression. CELF-1 contains three highly conserved RNA recognition motifs (RRMs), also known as RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains): two consecutive RRMs (RRM1 and RRM2) situated in the N-terminal region followed by a linker region and the third RRM (RRM3) close to the C-terminus of the protein. The two N-terminal RRMs of EDEN-BP are necessary for the interaction with EDEN as well as a part of the linker region (between RRM2 and RRM3). Oligomerization of EDEN-BP is required for specific mRNA deadenylation and binding. CELF-2 is expressed in all tissues at some level, but highest in brain, heart, and thymus. It has been implicated in the regulation of nuclear and cytoplasmic RNA processing events, including alternative splicing, RNA editing, stability and translation. CELF-2 shares high sequence identity with CELF-1, but shows different binding specificity; it preferentially binds to sequences with UG repeats and UGUU motifs. It has been shown to bind to a Bruno response element, a cis-element involved in translational control of oskar mRNA in Drosophila, and share sequence similarity to Bruno, the Drosophila protein that mediates this process. It also binds to the 3'-UTR of cyclooxygenase-2 messages, affecting both translation and mRNA stability, and binds to apoB mRNA, regulating its C to U editing. CELF-2 also contains three highly conserved RRMs. It binds to RNA via the first two RRMs, which are also important for localization in the cytoplasm. The splicing activation or repression activity of CELF-2 on some specific substrates is mediated by RRM1/RRM2. Both, RRM1 and RRM2 of CELF-2, can activate cardiac troponin T (cTNT) exon 5 inclusion. In addition, CELF-2 possesses a typical arginine and lysine-rich nuclear localization signal (NLS) in the C-terminus, within RRM3.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 182889006  61 EVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEG 128
Cdd:cd12634    3 KLFIGMVSKKCNENDIRVMFSPFGQIEECRILRGPDGLSRGCAFVTFSTRAMAQNAIKAMHQSQTMEG 70

RNA recognition motif 1 (RRM1) found in plant flowering time control protein FCA and similar proteins; This subgroup corresponds to the RRM1 of FCA, a gene controlling flowering time in Arabidopsis, encoding a flowering time control protein that functions in the posttranscriptional regulation of transcripts involved in the flowering process. FCA contains two RNA recognition motifs (RRMs), also known as RBDs (RNA binding domains) or RNP (ribonucleoprotein domains), and a WW protein interaction domain.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006  61 EVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTVrrstek 139
Cdd:cd12633    1 KLFVGSVPRTITEQEVRPMFEEHGNVLEVAIIKDkRTGHQQGCCFVKYSTRDEADRAIRALHNQRTLPGGASPV------ 74

                 ....*..
gi 182889006 140 rQLRLGD 146
Cdd:cd12633   75 -QVRYAD 80

RNA recognition motif 3 (RRM3) found in RNA-binding protein 45 (RBM45) and similar proteins; This subfamily corresponds to the RRM3 of RBM45, also termed developmentally-regulated RNA-binding protein 1 (DRB1), a new member of RNA recognition motif (RRM)-type neural RNA-binding proteins, which expresses under spatiotemporal control. It is encoded by gene drb1 that is expressed in neurons, not in glial cells. RBM45 predominantly localizes in cytoplasm of cultured cells and specifically binds to poly(C) RNA. It could play an important role during neurogenesis. RBM45 carries four RRMs, also known as RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains).

                         10        20        30
                 ....*....|....*....|....*....|....*....
gi 182889006  96 SGQTRGFAYAKYGDPLTASAAVTTLHQYRLPEGGCLTVR 134
Cdd:cd12368   37 TGKSKGFAYVTYNNPASAIYAKEKLNGFEYPPGNRLKVK 75

RNA recognition motif 1 (RRM1) found in the Hu proteins family; This subfamily corresponds to the RRM1 of the Hu proteins family which represents a group of RNA-binding proteins involved in diverse biological processes. Since the Hu proteins share high homology with the Drosophila embryonic lethal abnormal vision (ELAV) protein, the Hu family is sometimes referred to as the ELAV family. Drosophila ELAV is exclusively expressed in neurons and is required for the correct differentiation and survival of neurons in flies. The neuronal members of the Hu family include Hu-antigen B (HuB or ELAV-2 or Hel-N1), Hu-antigen C (HuC or ELAV-3 or PLE21), and Hu-antigen D (HuD or ELAV-4), which play important roles in neuronal differentiation, plasticity and memory. HuB is also expressed in gonads. Hu-antigen R (HuR or ELAV-1 or HuA) is the ubiquitously expressed Hu family member. It has a variety of biological functions mostly related to the regulation of cellular response to DNA damage and other types of stress. HuR has an anti-apoptotic function during early cell stress response. It binds to mRNAs and enhances the expression of several anti-apoptotic proteins, such as p21waf1, p53, and prothymosin alpha. HuR also has pro-apoptotic function by promoting apoptosis when cell death is unavoidable. Furthermore, HuR may be important in muscle differentiation, adipogenesis, suppression of inflammatory response and modulation of gene expression in response to chronic ethanol exposure and amino acid starvation. Hu proteins perform their cytoplasmic and nuclear molecular functions by coordinately regulating functionally related mRNAs. In the cytoplasm, Hu proteins recognize and bind to AU-rich RNA elements (AREs) in the 3' untranslated regions (UTRs) of certain target mRNAs, such as GAP-43, vascular epithelial growth factor (VEGF), the glucose transporter GLUT1, eotaxin and c-fos, and stabilize those ARE-containing mRNAs. They also bind and regulate the translation of some target mRNAs, such as neurofilament M, GLUT1, and p27. In the nucleus, Hu proteins function as regulators of polyadenylation and alternative splicing. Each Hu protein contains three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). RRM1 and RRM2 may cooperate in binding to an ARE. RRM3 may help to maintain the stability of the RNA-protein complex, and might also bind to poly(A) tails or be involved in protein-protein interactions.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 182889006  64 ISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTLHQYRL 125
Cdd:cd12650    5 VNYLPQNMTQDEIRSLFSSIGEIESCKLIRDkVTGQSLGYGFVNYVDPSDAEKAINTLNGLRL 67

RNA recognition motif 1 (RRM1) found in Schizosaccharomyces pombe mRNA export factor Crp79 and similar proteins; Crp79, also called meiotic expression up-regulated protein 5 (Mug5), or polyadenylate-binding protein crp79, or PABP, or poly(A)-binding protein, is an auxiliary mRNA export factor that binds the poly(A) tail of mRNA and is involved in the export of mRNA from the nucleus to the cytoplasm. Members in this family contain three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). The model corresponds to the first RRM motif.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 182889006  61 EVFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFS---GQTRGFAYAKYGDPLTASAAVTTLHQYRLpEGGCLTVR 134
Cdd:cd21619    3 TIYVGNIDMTINEDALEKIFSRYGQVESVRRPPIHTdkaDRTTGFGFIKYTDAESAERAMQQADGILL-GRRRLVVR 78

RNA recognition motif (RRM) found in heterogeneous nuclear ribonucleoprotein G (hnRNP G), Y chromosome RNA recognition motif 1 (hRBMY), testis-specific heterogeneous nuclear ribonucleoprotein G-T (hnRNP G-T) and similar proteins; This subfamily corresponds to the RRM domain of hnRNP G, also termed glycoprotein p43 or RBMX, an RNA-binding motif protein located on the X chromosome. It is expressed ubiquitously and has been implicated in the splicing control of several pre-mRNAs. Moreover, hnRNP G may function as a regulator of transcription for SREBP-1c and GnRH1. Research has shown that hnRNP G may also act as a tumor-suppressor since it upregulates the Txnip gene and promotes the fidelity of DNA end-joining activity. In addition, hnRNP G appears to play a critical role in proper neural development of zebrafish and frog embryos. The family also includes several paralogs of hnRNP G, such as hRBMY and hnRNP G-T (also termed RNA-binding motif protein, X-linked-like-2). Both, hRBMY and hnRNP G-T, are exclusively expressed in testis and critical for male fertility. Like hnRNP G, hRBMY and hnRNP G-T interact with factors implicated in the regulation of pre-mRNA splicing, such as hTra2-beta1 and T-STAR. Although members in this family share a high conserved N-terminal RNA recognition motif (RRM), also termed RBD (RNA binding domain) or RNP (ribonucleoprotein domain), they appear to recognize different RNA targets. For instance, hRBMY interacts specifically with a stem-loop structure in which the loop is formed by the sequence CA/UCAA. In contrast, hnRNP G associates with single stranded RNA sequences containing a CCA/C motif. In addition to the RRM, hnRNP G contains a nascent transcripts targeting domain (NTD) in the middle region and a novel auxiliary RNA-binding domain (RBD) in its C-terminal region. The C-terminal RBD exhibits distinct RNA binding specificity, and would play a critical role in the regulation of alternative splicing by hnRNP G.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|
gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMN-FSGQTRGFAYAKYGDPLTASAAVTTL 120
Cdd:cd12382    4 LFIGGLNTETNEKALEAVFGKYGRIVEVLLMKDrETNKSRGFAFVTFESPADAKDAARDM 63

RNA recognition motif 2 (RRM2) found in CUGBP Elav-like family member CELF-3, CELF-4, CELF-5, CELF-6 and similar proteins; This subgroup corresponds to the RRM2 of CELF-3, CELF-4, CELF-5, and CELF-6, all of which belong to the CUGBP1 and ETR-3-like factors (CELF) or BRUNOL (Bruno-like) family of RNA-binding proteins that display dual nuclear and cytoplasmic localizations and have been implicated in the regulation of pre-mRNA splicing and in the control of mRNA translation and deadenylation. CELF-3, expressed in brain and testis only, is also known as bruno-like protein 1 (BRUNOL-1), or CAG repeat protein 4, or CUG-BP- and ETR-3-like factor 3, or embryonic lethal abnormal vision (ELAV)-type RNA-binding protein 1 (ETR-1), or expanded repeat domain protein CAG/CTG 4, or trinucleotide repeat-containing gene 4 protein (TNRC4). It plays an important role in the pathogenesis of tauopathies. CELF-3 contains three highly conserved RNA recognition motifs (RRMs), also known as RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains): two consecutive RRMs (RRM1 and RRM2) situated in the N-terminal region followed by a linker region and the third RRM (RRM3) close to the C-terminus of the protein. The effect of CELF-3 on tau splicing is mediated mainly by the RNA-binding activity of RRM2. The divergent linker region might mediate the interaction of CELF-3 with other proteins regulating its activity or involved in target recognition. CELF-4, being highly expressed throughout the brain and in glandular tissues, moderately expressed in heart, skeletal muscle, and liver, is also known as bruno-like protein 4 (BRUNOL-4), or CUG-BP- and ETR-3-like factor 4. Like CELF-3, CELF-4 also contain three highly conserved RRMs. The splicing activation or repression activity of CELF-4 on some specific substrates is mediated by its RRM1/RRM2. On the other hand, both RRM1 and RRM2 of CELF-4 can activate cardiac troponin T (cTNT) exon 5 inclusion. CELF-5, expressed in brain, is also known as bruno-like protein 5 (BRUNOL-5), or CUG-BP- and ETR-3-like factor 5. Although its biological role remains unclear, CELF-5 shares same domain architecture with CELF-3. CELF-6, being strongly expressed in kidney, brain, and testis, is also known as bruno-like protein 6 (BRUNOL-6), or CUG-BP- and ETR-3-like factor 6. It activates exon inclusion of a cardiac troponin T minigene in transient transfection assays in a muscle-specific splicing enhancer (MSE)-dependent manner and can activate inclusion via multiple copies of a single element, MSE2. CELF-6 also promotes skipping of exon 11 of insulin receptor, a known target of CELF activity that is expressed in kidney. In addition to three highly conserved RRMs, CELF-6 also possesses numerous potential phosphorylation sites, a potential nuclear localization signal (NLS) at the C terminus, and an alanine-rich region within the divergent linker region.

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gi 182889006  73 EDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLH 121
Cdd:cd12635   15 EDDVRRLFEPFGSIEECTILRGPDGNSKGCAFVKFSSHAEAQAAINALH 63

RNA recognition motif 3 (RRM3) found in Saccharomyces cerevisiae protein HRB1, G-strand-binding protein 2 (GBP2) and similar proteins; The family includes Saccharomyces cerevisiae protein HRB1 (also called protein TOM34) and GBP2, both of which are SR-like mRNA-binding proteins which shuttle from the nucleus to the cytoplasm when bound to the mature mRNA molecules. They act as quality control factors for spliced mRNAs. GBP2, also called RAP1 localization factor 6, is a single-strand telomeric DNA-binding protein that binds single-stranded telomeric sequences of the type (TG[1-3])n in vitro. It also binds to RNA. GBP2 influences the localization of RAP1 in the nuclei and plays a role in modulating telomere length. Members in this family contain three RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains). The model corresponds to the third RRM motif.

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gi 182889006  62 VFISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQTRGFAYAKYGDPLTASAAVTTLHQYRLpeGGC 130
Cdd:cd21607    5 IYCSNLPLSTAESDLYDLFETIGKVNNAELKYDETGDPTGSAVVEYENLDDADVCISKLNNYNY--GGC 71

RNA recognition motif 2 (RRM2) found in plant flowering time control protein FCA and similar proteins; This subgroup corresponds to the RRM2 of FCA, a gene controlling flowering time in Arabidopsis, which encodes a flowering time control protein that functions in the posttranscriptional regulation of transcripts involved in the flowering process. The flowering time control protein FCA contains two RNA recognition motifs (RRMs), also known as RBDs (RNA binding domains) or RNP (ribonucleoprotein domains), and a WW protein interaction domain.

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gi 182889006  63 FISQIPNDVYEDRLIPLFQSIGTIYEFRLMMNFSGQT-RGFAYAKYGDPLTASAAVTTL 120
Cdd:cd12637    3 FVGSLPKTATEQEVRDLFEAYGEVEEVYLMKDPVTQQgTGCAFVKFAYKEEALAAIRSL 61