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

Cell. 1991 Sep 6;66(5):1015-26. doi: 10.1016/0092-8674(91)90445-5.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cell Cycle*
  • Cloning, Molecular
  • Cyclins / physiology*
  • DNA-Binding Proteins / physiology
  • Fungal Proteins / genetics*
  • Gene Expression Regulation, Fungal*
  • Genes, Lethal
  • Genes, Suppressor
  • Macromolecular Substances
  • Molecular Sequence Data
  • Protein Binding
  • RNA, Fungal / genetics
  • Regulatory Sequences, Nucleic Acid
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins*
  • Transcription Factors / physiology*
  • Transcription, Genetic*


  • Cyclins
  • DNA-Binding Proteins
  • Fungal Proteins
  • Macromolecular Substances
  • RNA, Fungal
  • SWI4 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • PCL1 protein, S cerevisiae

Associated data

  • GENBANK/M73966
  • GENBANK/M73967
  • GENBANK/M73968