Regulation of B-type cyclin proteolysis by Cdc28-associated kinases in budding yeast

EMBO J. 1997 May 15;16(10):2693-702. doi: 10.1093/emboj/16.10.2693.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • CDC28 Protein Kinase, S cerevisiae / metabolism*
  • Cell Cycle / physiology*
  • Chromatids
  • Cyclin B*
  • Cyclins / metabolism*
  • Fungal Proteins / metabolism
  • G1 Phase / physiology
  • G2 Phase / physiology
  • In Situ Hybridization
  • Mitosis / physiology
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins*


  • CLB2 protein, S cerevisiae
  • CLN1 protein, S cerevisiae
  • CLN3 protein, S cerevisiae
  • Cyclin B
  • Cyclins
  • Fungal Proteins
  • Saccharomyces cerevisiae Proteins
  • CDC28 Protein Kinase, S cerevisiae