1. Trypanosome cdc2-Related Kinase 9 Controls Spliced Leader RNA cap4 Methylation and Phosphorylation of RNA Polymerase II Subunit RPB1.
- Author
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Badjatia, Nitika, Ambrosio, Daniela L., Lee, Ju Huck, and Günzl, Arthur
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TRYPANOSOMA brucei , *RNA polymerases , *METHYLATION , *PHOSPHORYLATION , *TRANSCRIPTION factors - Abstract
Conserved from yeast to mammals, phosphorylation of the heptad repeat sequence Tyr¹-Ser²-Pro³-Thr4-Ser5-Pro6-Ser7 in the carboxy-terminal domain (CTD) of the largest RNA polymerase II (RNA Pol II) subunit, RPB1, mediates the enzyme's promoter escape and binding of RNA-processing factors, such as the m7G capping enzymes. The first critical step, Ser5 phosphorylation, is carried out by cyclin-dependent kinase 7 (CDK7), a subunit of the basal transcription factor TFIIH. Many early-diverged pro-tists, such as the lethal human parasite Ttypanosotna brucei, however, lack the heptad repeats and, apparently, a CDK7 ortholog. Accordingly, characterization of trypanosome TFIIH did not identify a kinase component. The T. brucei CTD, however, is phos-phorylated and essential for transcription. Here we show that silencing the expression of T. brucei cdc2-related kinase 9 (CRK9) leads to a loss of RPB1 phosphorylation. Surprisingly, this event did not impair RNA Pol II transcription or cotranscriptional m7G capping. Instead, we observed that CRK9 silencing led to a block of spliced leader (SL) trans splicing, an essential step in trypanosome mRNA maturation, that was caused by hypomethylation of the SL RNA's unique cap4. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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