Yeast cell-type regulation of DNA repair

The mating-type locus ( MAT ) in the yeast Saccharomyces cerevisiae provides information about whether cells are of the a or α mating type, and genes at this locus encode transcriptional regulators that determine the phenotypes associated with the different cell types 1 . In a /α diploid cells, the a 1/α2 repressor is formed, which inhibits haploid-specific gene expression and indirectly promotes meiosis. Mutations in SIR (silent information regulator) genes cause a loss of both heterochromatin and transcriptional silencing, resulting in the expression of cryptic a and α genes resident at the HML and HMR loci. As a result, sir mutant strains have the properties of a /α diploids.