Distinct Cdk9-phosphatase switches act on elongation factor Spt5 at the beginning and end of the RNA polymerase II transcription cycle
Ontology highlight
ABSTRACT: The Pol II transcription cycle is ordered by CDKs and phosphatases. In fission yeast, Cdk9 phosphorylates carboxy-terminal repeats (CTRs) of Spt5 while inhibiting PP1 during elongation. Transcription past the cleavage and polyadenylation signal (CPS) coincides with PP1-dependent Spt5 dephosphorylation and leads to Pol II pausing with phosphorylated CTD-Ser2 (pSer2). Here we show this switch is conserved in humans: Cdk9 inhibition decreases phosphorylation of both PP1g and Spt5-Thr806 (pThr806), and induces pSer2 upstream of the CPS, whereas PP1 depletion increases pThr806. Moreover, in unperturbed cells, pThr806 is diminished in 3’-paused complexes where pSer2 is maximal. Cdk9 also phosphorylates Spt5 on Ser666, a PP1-refractory site between conserved KOW4 and KOW5 motifs; pSer666 increases upon promoter-proximal pause release and, in contrast to pThr806, persists beyond the CPS. We identify PP4—another target of inhibitory phosphorylation by Cdk9—as a pSer666 phosphatase. PP4 and PP1g are enriched at 5’ and 3’ ends of genes, respectively, consistent with pSer666 and pThr806 distributions. Therefore, distinct Cdk9-phosphatase switches operate on Spt5 at different steps in transcription.
ORGANISM(S): Homo sapiens
PROVIDER: GSE138548 | GEO | 2020/08/04
REPOSITORIES: GEO
ACCESS DATA