Let's study ID: a demonstration of molecular processes (Introduction)

by David Turell @, Thursday, October 14, 2021, 23:07 (51 days ago) @ David Turell

Working out the stepwise molecular reactions:


"Control by RNA polymerase II
Evidence indicates that yeast cells initiate DNA synthesis and transition from the G1 to the S phase of the cell cycle when cyclin 3 accumulates and causes phosphorylation of Whi5, a functional equivalent of the mammalian Rb (retinoblastoma) protein. Kõivomägi et al. now present evidence for a different cyclin-dependent kinase target (see the Perspective by Fisher). They found that the cyclin 3–cyclin-dependent kinase (Cdk) 1 complex in yeast promoted phosphorylation of RNA polymerase II and thus increased transcription at genes that control entry into the cell cycle. Cdks that regulate the cell cycle can thus act by similar mechanisms to so-called “transcriptional Cdks,” which are known to act as transcriptional regulators but not to function in control of cell division.

Cell division is thought to be initiated by cyclin-dependent kinases (Cdks) inactivating key transcriptional inhibitors. In budding yeast, the G1 cyclin Cln3-Cdk1 complex is thought to directly phosphorylate the Whi5 protein, thereby releasing the transcription factor SBF and committing cells to division. We report that Whi5 is a poor substrate of Cln3-Cdk1, which instead phosphorylates the RNA polymerase II subunit Rpb1’s C-terminal domain on S5 of its heptapeptide repeats. Cln3-Cdk1 binds SBF-regulated promoters and Cln3’s function can be performed by the canonical S5 kinase Ccl1-Kin28 when synthetically recruited to SBF. Thus, we propose that Cln3-Cdk1 triggers cell division by phosphorylating Rpb1 at SBF-regulated promoters to promote transcription. Our findings blur the distinction between cell cycle and transcriptional Cdks to highlight the ancient relationship between these two processes."

Comment: Don't try to follow the steps. Just note how each step affects the next until a result is achieved. It is all automatic

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