Project description:Cyclin dependent kinases activation and RNA polymerase II transcription are linked by the Cdk7 kinase that phosphorylates Cdks as a trimeric CAK complex, and serine 5 within the PolII C-terminal domain (CTD) as TFIIH bound CAK. However, the physiological importance of integrating these processes is not understood. Beside the Cdk7 ortholog Mcs6, fission yeast possesses a second CAK, Csk1. Both enzymes were proposed to act redundantly to activate Cdc2. Using an improved analogue sensitive Mcs6-as kinase, we show that Csk1 is not a relevant CAK for Cdc2. Further analyses revealed that Csk1 lacks a 20 amino acid sequence required for its budding yeast counterpart, Cak1, to bind Cdc2. Transcriptome profiling of the Mcs6-as mutant in the presence or absence of the budding yeast Cak1 kinase, in order to uncouple the CTD kinase and CAK activities of Mcs6, revealed an unanticipated role of the CAK branch in the transcriptional control of the cluster of genes implicated in ribosome biogenesis and cell growth. The analysis of a Cdc2 CAK site mutant confirmed these data. Our data show that the Cdk7 kinase modulates transcription through both its well-described RNA Polymerase II CTD kinase activity, but also through the Cdc2 activating kinase activity.
Project description:We report that inactivation of the fission yeast Cdk7 kinase affects gene expression through both its RNA Polymerase II CTD kinase activity and its Cdc2-activating kinase activity. The ribosome biogenesis cluster is specifically downregulated when Cdc2 T167 phosphorylation is abolished, which results is slow growth. We propose that Cdc2 activation by CAK defines the rate change point observed in mid G2 and that CAK therefore couples cell growth to cell division. Total RNA was isolated from two biological replicates for all conditions, and each biological replicate was hybridized in duplicate on Agilent arrays (dye-swap).
