G1/S cyclin-dependent kinase regulates small GTPase Rho1p through phosphorylation of RhoGEF Tus1p in Saccharomyces cerevisiae

Mol Biol Cell. 2008 Apr;19(4):1763-71. doi: 10.1091/mbc.e07-09-0950. Epub 2008 Feb 6.


Rho1p is an essential small GTPase that plays a key role in the morphogenesis of Saccharomyces cerevisiae. We show here that the activation of Rho1p is regulated by a cyclin-dependent kinase (CDK). Rho1p is activated at the G1/S transition at the incipient-bud sites by the Cln2p (G1 cyclin) and Cdc28p (CDK) complex, in a process mediated by Tus1p, a guanine nucleotide exchange factor for Rho1p. Tus1p interacts physically with Cln2p/Cdc28p and is phosphorylated in a Cln2p/Cdc28p-dependent manner. CDK phosphorylation consensus sites in Tus1p are required for both Cln2p-dependent activation of Rho1p and polarized organization of the actin cytoskeleton. We propose that Cln2p/Cdc28p-dependent phosphorylation of Tus1p is required for appropriate temporal and spatial activation of Rho1p at the G1/S transition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Binding Sites
  • CDC28 Protein Kinase, S cerevisiae / genetics
  • CDC28 Protein Kinase, S cerevisiae / metabolism
  • Cell Division
  • Cyclin-Dependent Kinases / genetics
  • Cyclin-Dependent Kinases / metabolism*
  • Cyclins / genetics
  • Cyclins / metabolism
  • Enzyme Activation
  • G1 Phase
  • Genes, Fungal
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Models, Biological
  • Mutation
  • Phosphorylation
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • S Phase
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • rho GTP-Binding Proteins / genetics
  • rho GTP-Binding Proteins / metabolism*


  • Actins
  • CLN2 protein, S cerevisiae
  • Cyclins
  • Guanine Nucleotide Exchange Factors
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins
  • TUS1 protein, S cerevisiae
  • CDC28 Protein Kinase, S cerevisiae
  • Cyclin-Dependent Kinases
  • RHO1 protein, S cerevisiae
  • rho GTP-Binding Proteins