Repression of the yeast HO gene by the MATalpha2 and MATa1 homeodomain proteins.
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-alpha2 heterodimer, which represses HO and other haploid-specific genes in diploid yeast cells. We have determined that a1-alpha2 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-alpha2-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-alpha2 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-alpha2 prevents DNA binding by activator proteins resulting in repression of HO.
Mathias
Jonathan R
JR
Waksman Institute and Department of Molecular Biology and Biochemistry, 190 Frelinghuysen Road, Rutgers University, Piscataway, NJ 08854-8020, USA.
Hanlon
Sean E
SE
O'Flanagan
Ruadhan A
RA
Sengupta
Anirvan M
AM
Vershon
Andrew K
AK
D001483:Base Sequence; D001665:Binding Sites; D002453:Cell Cycle; D047369:Chromatin Immunoprecipitation; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D018398:Homeodomain Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D018398:Homeodomain Proteins; C096063:MATA1 protein, S cerevisiae; C062928:MATA2 protein, S cerevisiae; D009687:Nuclear Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C066502:TUP1 protein, S cerevisiae; C530845:HO protein, S cerevisiae; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific