PMS1 was identified by its homology to a yeast protein involved in DNA mismatch repair. A role for this protein in mismatch repair has not been proven. However, the protein forms heterodimers with MLH1, a DNA mismatch repair protein, and some cases of hereditary nonpolyposis colorectal cancer have been found to have mutations in this gene.

Sequence analysis of human PMS1 cDNA identified an open reading frame (ORF) of 2,795 bp thought to encode a 932-residue protein with 27% identity to yeast PMS1. Sequence analysis of the human PMS2 clone identified a 2,586-bp ORF thought to encode an 862-residue protein with 32% identity to yeast PMS1.