Human CWC22 escorts the helicase eIF4AIII to spliceosomes and promotes exon junction complex assembly

Isabelle Barbosa; Nazmul Haque; Francesca Fiorini; Charlotte Barrandon; Catherine Tomasetto; Marco Blanchette; Hervé Le Hir

doi:10.1038/nsmb.2380

Human CWC22 escorts the helicase eIF4AIII to spliceosomes and promotes exon junction complex assembly

Nat Struct Mol Biol. 2012 Oct;19(10):983-90. doi: 10.1038/nsmb.2380. Epub 2012 Sep 9.

Authors

Isabelle Barbosa¹, Nazmul Haque, Francesca Fiorini, Charlotte Barrandon, Catherine Tomasetto, Marco Blanchette, Hervé Le Hir

Affiliation

¹ Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique UMR8197, Paris, France.

PMID: 22961380
DOI: 10.1038/nsmb.2380

Abstract

The exon-junction complex (EJC) functionally links splicing to subsequent mRNA localization, translation and stability. Sequence-independent binding of the EJC core to RNA is ensured by the DEAD-box helicase eIF4AIII. Here, we identified the splicing factor CWC22 as a new eIF4AIII partner in flies and humans. CWC22 coexists with eIF4AIII in large protein complexes distinct from EJCs. Recombinant CWC22 directly contacts eIF4AIII and prevents it from binding RNA. In vitro splicing assays revealed that CWC22 introduces eIF4AIII to spliceosomes before remodeling to facilitate eIF4AIII incorporation into the EJC. Finally, using knockdowns in vivo, we showed that CWC22 is essential for EJC assembly. We elucidated the initial step of EJC assembly and the duality of CWC22 function that hinders eIF4AIII from nonspecifically binding RNA and escorts it to the splicing machinery to promote EJC assembly on mature mRNAs.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Sequence
Animals
Carrier Proteins / genetics
Carrier Proteins / metabolism*
DEAD-box RNA Helicases / genetics
DEAD-box RNA Helicases / metabolism*
DNA Repair Enzymes / genetics
DNA Repair Enzymes / metabolism
Eukaryotic Initiation Factor-4A / genetics
Eukaryotic Initiation Factor-4A / metabolism*
Exons*
Gene Knockdown Techniques
Humans
Molecular Sequence Data
Nuclear Proteins / genetics
Nuclear Proteins / metabolism
Peptidylprolyl Isomerase
Protein Interaction Domains and Motifs
Protein Structure, Tertiary
RNA / metabolism
RNA Splicing
RNA Splicing Factors
RNA, Messenger / metabolism
RNA-Binding Proteins
Recombinant Proteins / genetics
Recombinant Proteins / metabolism
Spliceosomes / metabolism*

Substances

CWC22 protein, human
Carrier Proteins
Nuclear Proteins
RNA Splicing Factors
RNA, Messenger
RNA-Binding Proteins
Recombinant Proteins
RNA
Eukaryotic Initiation Factor-4A
EIF4A3 protein, human
DEAD-box RNA Helicases
Peptidylprolyl Isomerase
DNA Repair Enzymes
PRPF19 protein, human