The MSH2 gene is composed of 16 exons spanning in a region of 80098 bp.

The transcribed mRNA has 3145 bp.

Aminoacids: 934. Molecular Weight: 104.7 kDa. MSH2 is a protein involved in the mismatch repair process after DNA replication. It contains a DNA binding domain and two interaction domains, one for MSH3 or MSH6 and the other for MutL homologs (MLH1 and PMS2), located in two different regions of the gene.

Nuclear

MSH2 can bind to MSH6 or to MSH3 to form the MutS alpha or the MutS beta complexes respectively. While MutS alpha complex binds to base-base and insertion-deletion mismatches, MutS beta only binds to insertion-deletion mismatches. Upon binding to the mismatch, the MutS complex associates with the MutL complex (composed of MLH1 and PMS2), and recruits the proteins needed for DNA excision and repair. (See also: Repair of DNA double-strand breaks

MSH2 is homologue to the bacterial MutS gene and MSH2 homologues are also present in eukaryotes.

There are over 300 MSH2 germline mutations described along the gene that cause hereditary non-polyposis colorectal cancer (HNPCC, see below). Mutations do not occur in any particular hotspot or region of the gene and include either nucleotide substitutions (missense, nonsense and splicing errors) and insertions/deletions (gross or small). In most of these mutations the resulting protein is truncated. Although rare there are described some founding mutations which account for a high proportion of the HNPCC tumours in some specific populations. Some germline genetic changes have also been described in exons and introns as non pathogenic.

Some sporadic mismatch repair deficient cases (sporadic MSI) with somatic MSH2 mutations are described.