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

de Bruin RA, McDonald WH, Kalashnikova TI, Yates J, Wittenberg C
Cell. 2004 117 (7): 887-98

PMID: 15210110 · DOI:10.1016/j.cell.2004.05.025

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.

MeSH Terms (20)

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, Genetic Transcriptional Activation Transcription Factors

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