The Saccharomyces cerevisiae Cdc68 transcription activator is antagonized by San1, a protein implicated in transcriptional silencing

Mol Cell Biol. 1993 Dec;13(12):7553-65. doi: 10.1128/mcb.13.12.7553-7565.1993.

Abstract

The CDC68 gene (also called SPT16) encodes a transcription factor for the expression of a diverse set of genes in the budding yeast Saccharomyces cerevisiae. To identify other proteins that are functionally related to the Cdc68 protein, we searched for genetic suppressors of a cdc68 mutation. Four suppressor genes in which mutations reverse the temperature sensitivity imposed by the cdc68-1 mutation were found. We show here that one of the suppressor genes is the previously reported SAN1 gene; san1 mutations were originally identified as suppressors of a sir4 mutation, implicated in the chromatin-mediated transcriptional silencing of the two mating-type loci HML and HMR. Each san1 mutation, including a san1 null allele, reversed all aspects of the cdc68 mutant phenotype. Conversely, increased copy number of the wild-type SAN1 gene lowered the restrictive temperature for the cdc68-1 mutation. Our findings suggest that the San1 protein antagonizes the transcriptional activator function of the Cdc68 protein. The identification of san1 mutations as suppressors of cdc68 mutations suggests a role for Cdc68 in chromatin structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Cell Cycle Proteins*
  • Cyclins / genetics
  • Fungal Proteins / genetics*
  • Genes, Fungal
  • Genes, Mating Type, Fungal
  • Genes, Suppressor
  • Histones / genetics
  • Mutation
  • Phenotype
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins*
  • Trans-Activators / genetics*
  • Transcription Factors*
  • Transcription, Genetic
  • Transcriptional Elongation Factors

Substances

  • Cell Cycle Proteins
  • Cyclins
  • Fungal Proteins
  • Histones
  • SPT16 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • Transcription Factors
  • Transcriptional Elongation Factors