Updating the rna polymerase ctd code
Speaker: Dr Shona Murphy Reader in Molecular Biology, Personnel Administrator and Academic Bursar, Oxford University Our research aims to elucidate the mechanisms underlying control of gene expression at the levels of transcription and co-transcriptional RNA processing, focusing recently on the role of co-transcriptional modification of the carboxyl-terminal domain (CTD) of RNA polymerase II.
We are using the human genes for the U1 and U2 small nuclear (sn)RNAs involved in splicing as model gene systems to study the coupling between dynamic CTD phosphorylation and gene expression.
The TFIIH-associated kinase Kin28 phosphorylates Ser5 (shown in red) and Ser7 (shown in purple) on the CTD.
Mediator-associated kinase Srb10 also contributes to the phosphorylation of Ser5-P.
To explore this issue, we applied high-throughput RNA sequencing methods (RNAseq) to gauge globally the impact of the loss of each of the four inessential CTD phosphoacceptors on gene expression.
We have shown how capping is directed to nascent Pol2 transcripts via physical interactions of one or more of the capping enzymes with the carboxyl-terminal domain (CTD) of the Pol2 Rpb1 subunit.
The RNA triphosphatase (TPase) components of the mammalian and budding yeast capping apparatus are recruited passively to the Pol2 CTD, by virtue of their physical association with the GTase: in has a distinctive strategy for targeting cap formation to Pol2 transcripts, whereby the TPase (Pct1) and GTase (Pce1) enzymes are not associated physically, but instead bind independently to the Ser5-phosphorylated Pol2 CTD Capping enzymes can also access nascent Pol2 transcripts via physical interactions with transcription elongation factor Spt5.
Spt5 is a large polypeptide, composed of multiple domain modules, that associates with the Pol2 transcription complex shortly after initiation and can exert negative and positive effects on transcription elongation.
(ii) which essential coding information is read by which essential CTD receptors?
We envisioned that genetics could assign an essential CTD coding letter to a specific CTD-receptor pair in the sea of available cellular receptors, if one could bypass the requirement for that letter by delivering a cognate receptor protein to the Pol2 transcription complex via other means.