Regulation of B-type cyclin proteolysis by Cdc28-associated kinases in budding yeast.
In budding yeast, stability of the mitotic B-type cyclin Clb2 is tightly cell cycle-regulated. B-type cyclin proteolysis is initiated during anaphase and persists throughout the G1 phase. Cln-Cdc28 kinase activity at START is required to repress B-type cyclin-specific proteolysis. Here, we show that Clb-dependent kinases, when expressed during G1, are also capable of repressing the B-type cyclin proteolysis machinery. Furthermore, we find that inactivation of Cln- and Clb-Cdc28 kinases is sufficient to trigger Clb2 proteolysis and sister-chromatid separation in G2/M phase-arrested cells, where the B-type cyclin-specific proteolysis machinery is normally inactive. Our results suggest that Cln- and Clb-dependent kinases are both capable of repressing B-type cyclin-specific proteolysis and that they are required to maintain the proteolysis machinery in an inactive state in S and G2/M phase-arrested cells. We propose that in yeast, as cells pass through START, Cln-Cdc28-dependent kinases inactivate B-type cyclin proteolysis. As Cln-Cdc28-dependent kinases decline during G2, Clb-Cdc28-dependent kinases take over this role, ensuring that B-type cyclin proteolysis is not activated during S phase and early mitosis.
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Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D002842:Chromatids; D019926:Cyclin B; D016213:Cyclins / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology; D016195:G2 Phase / Q000502:physiology; D017403:In Situ Hybridization; D008938:Mitosis / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins
C093749:CLB2 protein, S cerevisiae; C082719:CLN1 protein, S cerevisiae; C079895:CLN3 protein, S cerevisiae; D019926:Cyclin B; D016213:Cyclins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D017489:CDC28 Protein Kinase, S cerevisiae