G1 transcription factors are differentially regulated in Saccharomyces cerevisiae by the Swi6-binding protein Stb1.
Stage-specific transcriptional programs are an integral feature of cell cycle regulation. In the budding yeast Saccharomyces cerevisiae, over 120 genes are coordinately induced in late G(1) phase by two heterodimeric transcription factors called SBF and MBF. Activation of SBF and MBF is an upstream initiator of key cell cycle events, including budding and DNA replication. SBF and MBF regulation is complex and genetically redundant, and the precise mechanism of G(1) transcriptional activation is unclear. Assays using SBF- and MBF-specific reporter genes revealed that the STB1 gene specifically affected MBF-dependent transcription. STB1 encodes a known Swi6-binding protein, but an MBF-specific function had not been previously suspected. Consistent with a specific role in regulating MBF, a STB1 deletion strain requires SBF for viability and microarray studies show a decrease in MBF-regulated transcripts in a swi4Delta mutant following depletion of Stb1. Chromatin immunoprecipitation experiments confirm that Stb1 localizes to promoters of MBF-regulated genes. Our data indicate that, contrary to previous models, MBF and SBF have unique components and might be distinctly regulated.
Costanzo
Michael
M
Department of Medical Genetics and Microbiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
Schub
Oliver
O
Andrews
Brenda
B
D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D009154:Mutation; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
C082719:CLN1 protein, S cerevisiae; C082721:CLN2 protein, S cerevisiae; D016213:Cyclins; D004268:DNA-Binding Proteins; C083209:MBP1 protein, S cerevisiae; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; C120525:STB1 protein, S cerevisiae; C062214:SWI4 protein, S cerevisiae; C075111:SWI6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D017489:CDC28 Protein Kinase, S cerevisiae