MLH2, one of four MutL homologs in S. cerevisiae, is involved in mismatch repair during mitosis and meiosis and plays a role in correcting mismatches that arise during the formation of heteroduplex DNA between two homologous chromosomes during meiotic recombination (reviewed in 4, 5). Like Pms1p and Mlh3p, two other MutL homologs, Mlh2p forms a heterodimer with Mlh1p, the fourth MutL homolog (6, 7, 8, 2). Although mlh2 single mutants are resistant to some anticancer compounds (9) and are involved in the repair of specific types of mismatches (1), its role in general mismatch repair appears to be limited. In mlh2 single mutants, there is an increase in events where the 4:4 Mendelian segregation pattern of the 8 single-strands of DNA is altered to a 5:3 non-Mendelian segregation pattern, suggesting mlh2 mutants fail to repair these mismatches during meiosis (2, 3). Although mlh2 single mutants do not display a decrease in the level of cross-overs like an mlh3 single mutant, an mlh2 mlh3 double mutant displays an increase in the level of cross-overs compared to the mlh3 single mutant, suggesting that Mlh2p may play a role in the formation of heteroduplexes that lead to cross-overs (3).

Last updated: 2007-05-29