Repression of the yeast HO gene by the MATα2 and MATa1 homeodomain proteins

Jonathan R. Mathias, Sean E. Hanlon, Ruadhan A. O'Flanagan, Anirvan M. Sengupta, Andrew K. Vershon

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


The HO gene in Saccharomyces cerevisiae is regulated by a large and complex promoter that is similar to promoters in higher order eukaryotes. Within this promoter are 10 potential binding sites for the a1-α2 heterodimer, which represses HO and other haploid-specific genes in diploid yeast cells. We have determined that a1-α2 binds to these sites with differing affinity, and that while certain strong-affinity sites are crucial for repression of HO, some of the weak-affinity sites are dispensable. However, these weak-affinity a1-α2-binding sites are strongly conserved in related yeast species and have a role in maintaining repression upon the loss of strong-affinity sites. We found that these weak sites are sufficient for a1-α2 to partially repress HO and recruit the Tup1-Cyc8 (Tup1-Ssn6 co-repressor complex to the HO promoter. We demonstrate that the Swi5 activator protein is not bound to URS1 in diploid cells, suggesting that recruitment of the Tup1-Cyc8 complex by a1-α2 prevents DNA binding by activator proteins resulting in repression of HO.

Original languageEnglish (US)
Pages (from-to)6469-6478
Number of pages10
JournalNucleic acids research
Issue number22
StatePublished - 2004

All Science Journal Classification (ASJC) codes

  • Genetics

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