Cellular physiology of mismatch repair.

The DNA mismatch repair system maintains genomic stability by correcting DNA sequence errors generated during DNA replication, during genetic exchanges between chromosomes i.e., recombination, and by correcting DNA lesions caused by mutagenic agents such as cis-platinum. Post-synthesis mismatch repair improves almost 1000-fold the fidelity of DNA replication; however, the functions of mismatch repair proteins extend well beyond DNA repair. Recent studies suggest that mismatch repair is part of the machinery that couples DNA damage and repair to cell cycle regulation and apoptosis. These studies indicate that tolerance to certain DNA lesions (such as methylation and cis-platinum adducts) is associated with inefficient activation of cell cycle checkpoints and inefficient activation of apoptosis in mismatch repair deficient cells. Hence, mismatch repair proteins regulate the survival threshold to DNA damage, and this function provides a novel platform for understanding the role of mismatch repair in B cells, in tumor formation, as well as in resistance to chemotherapy. In this communication, we review how mismatch repair may contribute to the physiology of cells and may be regulated by the intracellular trafficking of mismatch repair proteins.