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The EMBO Journal
(1997) 16, 2693–2702, doi:10.1093/emboj/16.10.2693
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| Regulation of B-type cyclin proteolysis by Cdc28–associated kinases in budding yeast |
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Angelika Amon
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Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
Received 20 November 1996; Revised 20 January 1997.
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| Abstract |
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| 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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| Keywords: Cdc28-dependent kinases, Clb2, cyclin B proteolysis, Saccharomyces cerevisiae, Sic1 |
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