Unconventional rules of small nuclear RNA transcription and cap modification in trypanosomatids

Gene Expr. 2002;10(1-2):3-16.

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

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Dinucleoside Phosphates / metabolism
  • Evolution, Molecular
  • Genes
  • Genes, Overlapping
  • Methyltransferases / metabolism
  • Promoter Regions, Genetic
  • Protozoan Proteins / metabolism
  • RNA Caps / metabolism*
  • RNA Polymerase II / metabolism
  • RNA Precursors / genetics
  • RNA Precursors / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA Splicing*
  • RNA, Protozoan / genetics
  • RNA, Protozoan / physiology*
  • RNA, Small Nuclear / genetics
  • RNA, Small Nuclear / metabolism*
  • RNA, Spliced Leader / genetics
  • RNA, Spliced Leader / physiology*
  • RNA, Transfer / genetics
  • Regulatory Sequences, Nucleic Acid
  • Ribonucleoproteins, Small Nuclear / metabolism
  • Species Specificity
  • Spliceosomes / metabolism
  • Transcription, Genetic*
  • Trypanosoma brucei brucei / genetics
  • Trypanosomatina / genetics*

Substances

  • Dinucleoside Phosphates
  • Protozoan Proteins
  • RNA Caps
  • RNA Precursors
  • RNA, Protozoan
  • RNA, Small Nuclear
  • RNA, Spliced Leader
  • Ribonucleoproteins, Small Nuclear
  • 7-methyl-diguanosine triphosphate
  • RNA, Transfer
  • 16S rRNA - m7G methyltransferase
  • Methyltransferases
  • RNA Polymerase II