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Cln3 activates G1-specific transcription via phosphorylation of the SBF bound repressor Whi5.

G1-specific transcriptional activation by Cln3/CDK initiates the budding yeast cell cycle. To identify targets of Cln3/CDK, we analyzed the SBF and MBF transcription factor complexes by multidimensional protein interaction technology (MudPIT). Whi5 was identified as a stably bound component of SBF but not MBF. Inactivation of Whi5 leads to premature expression of G1-specific genes and budding, whereas overexpression retards those processes. Whi5 inactivation bypasses the requirement for Cln3 both for transcriptional activation and cell cycle initiation. Whi5 associates with G1-specific promoters via SBF during early G1 phase, then dissociates coincident with transcriptional activation. Dissociation of Whi5 is promoted by Cln3 in vivo. Cln/CDK phosphorylation of Whi5 in vitro promotes its dissociation from SBF complexes. Mutation of putative CDK phosphorylation sites, at least five of which are phosphorylated in vivo, strongly reduces SBF-dependent transcription and delays cell cycle initiation. Like mammalian Rb, Whi5 is a G1-specific transcriptional repressor antagonized by CDK.

Pubmed ID: 15210110


  • de Bruin RA
  • McDonald WH
  • Kalashnikova TI
  • Yates J
  • Wittenberg C



Publication Data

June 25, 2004

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM59941

Mesh Terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Cell Size
  • Chromatin
  • Consensus Sequence
  • Cyclins
  • G1 Phase
  • Gene Expression Regulation, Fungal
  • Models, Genetic
  • Molecular Sequence Data
  • Phosphorylation
  • Precipitin Tests
  • Promoter Regions, Genetic
  • Repressor Proteins
  • Reverse Transcriptase Polymerase Chain Reaction
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Transcription, Genetic
  • Transcriptional Activation