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Cell. 1991 Sep 6;66(5):1015-26.

Transcriptional activation of CLN1, CLN2, and a putative new G1 cyclin (HCS26) by SWI4, a positive regulator of G1-specific transcription.

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1
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.

Abstract

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.

PMID:
1832336
[Indexed for MEDLINE]

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