Activation of basal transcription by a mutation in SIN4, a yeast global repressor, occurs through a mechanism different from activator-mediated transcriptional enhancement

Mol Gen Genet. 2000 Feb;263(1):48-59. doi: 10.1007/pl00008675.

Abstract

The Saccharomyces cerevisiae protein Sin4 has been suggested to affect the transcription of various genes by locally altering chromatin structure. Previous studies have defined two classes of promoters: those which are activated by loss of SIN4 function (termed sin4-responsive promoters) and those which are not activated by sin4 mutations (termed sin4 non-responsive promoters). We analyzed the mechanism of this differential response of the two classes of promoters to a sin4 mutation. The sin4 non-responsive promoters were activated when upstream elements in the promoter region were eliminated. The upstream elements of sin4 non-responsive promoters were, in turn, found to repress the activity of the sin4-responsive promoters in an orientation-independent manner. The sin4-mediated activation was repressed by the Rme1- but not by the Tup1-Ssn6-mediated repression system. Activation of sin4-responsive promoters by Pho4 and the sin4 mutation was additive, and enhancement of transcription driven by sin4-responsive promoters was found to be due to an increase in the basal rate of transcription. The upstream regions in the sin4 non-responsive promoters contained elements that were able to inhibit activation of basal transcription. Based on these observations, we suggest that activation of basal transcription by a mutation in a gene for a global repressor, SIN4, occurs through a mechanism that differs from that responsible for activator-mediated transcriptional enhancement, and we therefore propose that basal transcription and activator-mediated transcription are repressed by different mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • DNA Primers / genetics
  • DNA, Fungal / genetics
  • DNA-Binding Proteins*
  • Fungal Proteins / genetics*
  • Genes, Fungal
  • Genes, Reporter
  • Mediator Complex
  • Models, Genetic
  • Mutation*
  • Open Reading Frames
  • Plasmids / genetics
  • Promoter Regions, Genetic
  • Repressor Proteins / genetics*
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins*
  • Trans-Activators*
  • Transcription Factors*
  • Transcriptional Activation

Substances

  • DNA Primers
  • DNA, Fungal
  • DNA-Binding Proteins
  • Fungal Proteins
  • Mediator Complex
  • PHO4 protein, S cerevisiae
  • Repressor Proteins
  • SIN4 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Trans-Activators
  • Transcription Factors