Ash1 and Tup1 dependent repression of the Saccharomyces cerevisiae HO promoter requires activator-dependent nucleosome eviction

PLoS Genet. 2020 Dec 31;16(12):e1009133. doi: 10.1371/journal.pgen.1009133. eCollection 2020 Dec.

Abstract

Transcriptional regulation of the Saccharomyces cerevisiae HO gene is highly complex, requiring a balance of multiple activating and repressing factors to ensure that only a few transcripts are produced in mother cells within a narrow window of the cell cycle. Here, we show that the Ash1 repressor associates with two DNA sequences that are usually concealed within nucleosomes in the HO promoter and recruits the Tup1 corepressor and the Rpd3 histone deacetylase, both of which are required for full repression in daughters. Genome-wide ChIP identified greater than 200 additional sites of co-localization of these factors, primarily within large, intergenic regions from which they could regulate adjacent genes. Most Ash1 binding sites are in nucleosome depleted regions (NDRs), while a small number overlap nucleosomes, similar to HO. We demonstrate that Ash1 binding to the HO promoter does not occur in the absence of the Swi5 transcription factor, which recruits coactivators that evict nucleosomes, including the nucleosomes obscuring the Ash1 binding sites. In the absence of Swi5, artificial nucleosome depletion allowed Ash1 to bind, demonstrating that nucleosomes are inhibitory to Ash1 binding. The location of binding sites within nucleosomes may therefore be a mechanism for limiting repressive activity to periods of nucleosome eviction that are otherwise associated with activation of the promoter. Our results illustrate that activation and repression can be intricately connected, and events set in motion by an activator may also ensure the appropriate level of repression and reset the promoter for the next activation cycle.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Deoxyribonucleases, Type II Site-Specific / genetics*
  • Deoxyribonucleases, Type II Site-Specific / metabolism
  • Gene Expression Regulation, Fungal
  • Histone Deacetylases / genetics
  • Histone Deacetylases / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Nucleosomes / metabolism*
  • Promoter Regions, Genetic*
  • Protein Binding
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcriptional Activation

Substances

  • ASH1 protein, S cerevisiae
  • Cell Cycle Proteins
  • Nuclear Proteins
  • Nucleosomes
  • Repressor Proteins
  • SWI5 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • TUP1 protein, S cerevisiae
  • Transcription Factors
  • HO protein, S cerevisiae
  • Deoxyribonucleases, Type II Site-Specific
  • RPD3 protein, S cerevisiae
  • Histone Deacetylases