Mismatch repair contributes to the overall fidelity of DNA replication []. It involves the correction of mismatched base pairs that have been missed by the proofreading element of the DNA polymerase complex. The sequence of some proteins involved in mismatch repair in different organisms have been found to be evolutionarily related. These proteins include:Escherichia coli and Salmonella typhimurium mutL protein []. MutL is required for dam-dependent methyl-directed DNA repair.Streptococcus pneumoniae hexB protein []. The Hex system is nick directed.Yeast proteins PMS1 and MLH1 [].Human protein MLH1 []which is involved in a form of familial hereditary nonpolyposis colon cancer (HNPCC).This entry represents a perfectly conserved heptapeptide which is located in the N-terminal sectionof these proteins.
Mismatch repair is one of five major DNA repair pathways, the others being homologous recombination repair, non-homologous end joining, nucleotide excision repair, and base excision repair. The mismatch repair system recognises and repairs mispaired or unpaired nucleotides that result from errors in DNA replication. Many proteins involved in the different repair processes also play a role in apoptosis when DNA damage is excessive, thereby helping to prevent carcinogenesis []. The mismatch repair protein, Mlh1 (mutL homologue 1), has a dual role in DNA repair and apoptosis. Mlh1 acts as a heterodimer in conjunction with Pms2, Pms1 (post-meiotic segregation 1 and 2) or Mlh3 (MutL homologue 3), which function as adaptor proteins that link Msh (MutS homologue) heterodimers to the DNA repair machinery, resulting in excision and repair of the mispaired base [].This entry represents the mismatch repair protein MutL.
