DNA-mismatch repair (MMR) is an essential process in maintaining genetic stability. Lack of a functional DNA-mismatch repair pathway is a common characteristic of several different types of human cancers, either due to an MMR gene mutation or promoter methylation gene silencing. MLH1 is the human homologue of the E. coli MMR gene mutL. MMR requires recognition of a base mismatch or insertion/deletion loop by a MutS homolog followed by recruitment of a MutL heterodimeric complex consisting of MLH1 and PMS1 (MutL-γ), PMS2 (MutL-α) or MLH3 (MutL-γ). MLH1 also plays a role in meiotic recombination.
