Ma Z, Atencio D, Barnes C, Defiglio H, Hanes SD

The Ess1 prolyl isomerase in Saccharomyces cerevisiae regulates RNA polymerase II (pol II) by isomerizing peptide bonds within the pol II CTD heptapeptide repeat (YSPTSPS). Ess1 preferentially targets the Ser5-Pro6 bond when Ser5 is phosphorylated. Conformational changes in the CTD induced by Ess1 control the recruitment of essential co-factors to ...

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the pol II complex, and may facilitate the ordered transition between initiation, elongation, termination and RNA processing. Here, we show that Ess1 associates with the phospho-Ser5 form of polymerase in vivo, is present along the entire length of coding genes, and is critical for regulating phosphorylation of Ser7 within the CTD. In addition, Ess1 represses initiation of cryptic unstable transcripts (CUTs), and is required for efficient termination of mRNA transcription. Analysis using strains lacking non-sense mediated decay suggest as many as half of all yeast genes depend on Ess1 for efficient termination. Finally, we show that Ess1 is required for trimethylation of histone H3K4. Thus, Ess1 has direct effects on RNA polymerase transcription by controlling co-factor binding via conformationally-induced changes in the CTD, and indirect effects by influencing chromatin modification.

Date: Jul. 09, 2012

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