Transcriptional activation of CLN1, CLN2, and a putative new G1 cyclin (HCS26) by SWI4, a positive regulator of G1-specific transcription.
SWI4 of budding yeast codes for a component of a transcription factor (cell cycle box factor, or CCBF) necessary for G1-specific expression of HO. We show that SWI4 is essential for haploid cell viability at high temperature and in a/alpha cells at all temperatures: SWI4-deficient cells arrest as large unbudded cells. Eight high copy number plasmids were identified that allow swi4- strains to grow under nonpermissive conditions. Two carry G1 cyclin genes, CLN1 and CLN2; another carries HCS26, coding for a putative cyclin, a/alpha swi4- mutants exhibit 3- to 20-fold reductions in the levels of CLN1, CLN2, and HCS26 transcripts. The requirement of SWI4 for transcription appears to be direct: each gene contains sites similar to the CCBF-binding site; CCBF binds to the upstream region of HCS26. We propose that SWI4 participates in a positive feedback loop by which CLN1, CLN2, and possibly HCS26 promote their own transcription in G1.
Ogas
J
J
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
Andrews
B J
BJ
Herskowitz
I
I
D000595:Amino Acid Sequence; D001483:Base Sequence; D002453:Cell Cycle; D003001:Cloning, Molecular; D016213:Cyclins / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D005804:Genes, Lethal; D016153:Genes, Suppressor; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D011485:Protein Binding; D012331:RNA, Fungal / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D016213:Cyclins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D046911:Macromolecular Substances; D012331:RNA, Fungal; C062214:SWI4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C070839:PCL1 protein, S cerevisiae