@article {Tschudi:2002:1052-2166:3, title = "Unconventional Rules of Small Nuclear RNA Transcription and Cap Modification in Trypanosomatids", journal = "Gene Expression", parent_itemid = "infobike://cog/ge", publishercode ="cog", year = "2002", volume = "10", number = "1-2", publication date ="2002-01-01T00:00:00", pages = "3-16", itemtype = "ARTICLE", issn = "1052-2166", eissn = "1555-3884", url = "https://www.ingentaconnect.com/content/cog/ge/2002/00000010/f0020001/ge175", doi = "doi:10.3727/096020197390040", keyword = "Spliced leader RNA trans-Splicing Cap formation Ca", author = "Tschudi, C. and Ullu, E.", 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.", }