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bioRxiv · 10.1101/2021.03.25.436872

Localized phosphorylation of RNA Polymerase II by G1 cyclin-Cdk promotes cell cycle entry

Koivomagi, M.·Swaffer, M. P.·Turner, J. J.·Marinov, G. K.·Skotheim, J. M.
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Abstract

The cell cycle is thought to be initiated by cyclin-dependent kinases (Cdk) inactivating transcriptional inhibitors of cell cycle gene-expression(1, 2). In budding yeast, the G1 cyclin Cln3-Cdk1 complex is thought to directly phosphorylate Whi5, thereby releasing the transcription factor SBF and committing cells to division(3-7). Here, we report that Cln3-Cdk1 does not phosphorylate Whi5, but instead phosphorylates the RNA Polymerase II subunit Rpb1s C-terminal domain (CTD) on S5 of its heptapeptide repeats. Cln3-Cdk1 binds SBF-regulated promoters(8) and Cln3s function can be performed by the canonical S5 kinase(9) Ccl1-Kin28 when synthetically recruited to SBF. Thus, Cln3-Cdk1 triggers cell division by phosphorylating Rpb1 at SBF-regulated promoters to activate transcription. Our findings blur the distinction between cell cycle and transcriptional Cdks to highlight the ancient relationship between these processes.

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Koivomagi, M., Swaffer, M. P., Turner, J. J., Marinov, G. K., Skotheim, J. M.. 2021-03-25. Localized phosphorylation of RNA Polymerase II by G1 cyclin-Cdk promotes cell cycle entry. https://doi.org/10.1101/2021.03.25.436872

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