The Cln3-Cdc28 kinase complex of S. cerevisiae is regulated by proteolysis and phosphorylation

EMBO J. 1992 May;11(5):1773-84.


In Saccharomyces cerevisiae, several of the proteins involved in the Start decision have been identified; these include the Cdc28 protein kinase and three cyclin-like proteins, Cln1, Cln2 and Cln3. We find that Cln3 is a very unstable, low abundance protein. In contrast, the truncated Cln3-1 protein is stable, suggesting that the PEST-rich C-terminal third of Cln3 is necessary for rapid turnover. Cln3 associates with Cdc28 to form an active kinase complex that phosphorylates Cln3 itself and a co-precipitated substrate of 45 kDa. The cdc34-2 allele, which encodes a defective ubiquitin conjugating enzyme, dramatically increases the kinase activity associated with Cln3, but does not affect the half-life of Cln3. The Cln--Cdc28 complex is inactivated by treatment with non-specific phosphatases; prolonged incubation with ATP restores kinase activity to the dephosphorylated kinase complex. It is thus possible that phosphate residues essential for Cln-Cdc28 kinase activity are added autocatalytically. The multiple post-translational controls on Cln3 activity may help Cln3 tether division to growth.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Sequence
  • Blotting, Northern
  • Blotting, Western
  • CDC2 Protein Kinase / metabolism
  • CDC28 Protein Kinase, S cerevisiae*
  • Cell Cycle
  • Enzyme Stability
  • Hydrolysis
  • Molecular Sequence Data
  • Phosphorylation
  • Precipitin Tests
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Protein Processing, Post-Translational
  • RNA, Messenger / metabolism
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Ubiquitins / metabolism


  • RNA, Messenger
  • Ubiquitins
  • Protein Kinases
  • CDC2 Protein Kinase
  • CDC28 Protein Kinase, S cerevisiae
  • Cln3-Cdc28 kinase complex, S cerevisiae