Abstract
This review focuses on the spliced leader (SL) RNA and uridylic acid-rich small nuclear RNAs (U-snRNAs) involved in pre-mRNA processing in trypanosomatid protozoa, with particular emphasis on the mechanism of transcription and cap formation. The SL RNA plays a central role in mRNA biogenesis by providing the unique cap 4 structure to the 5' end of all mRNAs by trans-splicing. The trimethylguanosine capped U-snRNAs, on the other hand, represent an unusual example among eukaryotic snRNAs in that they are transcribed by RNA polymerase III. This implies the existence of a distinctive mechanism for capping enzyme selection by the transcriptional machinery. Furthermore, the transcription units of U-snRNA genes offer yet another example of the variety of choices that have been established during eukaryotic evolution, namely that an upstream tRNA gene or tRNA-like gene provides extragenic promoter elements for a downstream small RNA gene.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
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Review
MeSH terms
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Animals
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Dinucleoside Phosphates / metabolism
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Evolution, Molecular
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Genes
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Genes, Overlapping
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Methyltransferases / metabolism
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Promoter Regions, Genetic
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Protozoan Proteins / metabolism
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RNA Caps / metabolism*
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RNA Polymerase II / metabolism
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RNA Precursors / genetics
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RNA Precursors / metabolism
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RNA Processing, Post-Transcriptional
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RNA Splicing*
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RNA, Protozoan / genetics
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RNA, Protozoan / physiology*
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RNA, Small Nuclear / genetics
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RNA, Small Nuclear / metabolism*
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RNA, Spliced Leader / genetics
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RNA, Spliced Leader / physiology*
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RNA, Transfer / genetics
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Regulatory Sequences, Nucleic Acid
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Ribonucleoproteins, Small Nuclear / metabolism
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Species Specificity
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Spliceosomes / metabolism
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Transcription, Genetic*
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Trypanosoma brucei brucei / genetics
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Trypanosomatina / genetics*
Substances
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Dinucleoside Phosphates
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Protozoan Proteins
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RNA Caps
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RNA Precursors
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RNA, Protozoan
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RNA, Small Nuclear
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RNA, Spliced Leader
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Ribonucleoproteins, Small Nuclear
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7-methyl-diguanosine triphosphate
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RNA, Transfer
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16S rRNA - m7G methyltransferase
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Methyltransferases
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RNA Polymerase II