Role of the Recombination Enhancer in mating‐type switching in budding yeast

Abstract

DNA double‐strand breaks (DSB) can be repaired by two major processes: nonhomologous end‐joining and homologous recombination. In budding yeast, repair of DSB repair occurs by gene conversion (GC) if both ends of the DSB share homology with another DNA sequence. The Saccharomyces cerevisiae mating‐type switching includes formation of a controlled DSB at the MAT locus and repair from one of two donors, HML and HMR, through the GC repair mechanism. Donor preference has been shown to be highly biased so that MATa cells recombine preferentially with HMLα and MATα cells with HMRa. This bias is determined by a ~700 bp, cis‐acting region called the Recombination Enhancer (RE). Preliminary experiments show that in the absence of RE, initiation of DNA synthesis and subsequent repair of the break is strikingly delayed. We propose that the RE region plays an important role in regulating kinetics of MAT switching.