Abstract
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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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CDC28 Protein Kinase, S cerevisiae / genetics
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CDC28 Protein Kinase, S cerevisiae / metabolism*
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Cell Division / genetics
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Cell Division / physiology*
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Cyclins / genetics
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Cyclins / metabolism*
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G1 Phase / genetics
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G1 Phase / physiology
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Gene Expression Regulation, Fungal
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Phosphorylation
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Promoter Regions, Genetic
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Protein Domains
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RNA Polymerase II / chemistry
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RNA Polymerase II / metabolism*
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Repressor Proteins / metabolism
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae / physiology*
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Transcription Factors / metabolism
Substances
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CLN3 protein, S cerevisiae
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Cyclins
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Repressor Proteins
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SBF protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Transcription Factors
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Whi5 protein, S cerevisiae
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CDC28 Protein Kinase, S cerevisiae
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RNA Polymerase II
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RPB1 protein, S cerevisiae