Interpretations Mismatch repair systems in procaryotes and eucaryotes are similar in the recognition of damage and in the mode of damage removal . The systems primarily repair undamaged, but mismatched, base pairs and small insertions or deletions. Some modified bases, such as O-methylguanine are also recognized. In E. coli , mismatch repair is also methyl-directed repair , the methylation pattern directing the repair system to correct the newly synthesized strand, sparing the template strand. In eucaryotes, the role of methylation in directing repair is uncertain.
Repair is directed by nicks.
Nicks are normally present in the daughter strands during DNA replication and could thus provide the needed specificity. Mismatches resulting from base damage may lead to mutations if recognized by the mismatch repair system instead of BER or NER . This may account for the effectiveness of MNU and MNNG as mutagens . Further information Heteroduplexes resulting from strand exchange in recombination are also substrates for mismatch repair. The GTBP partner of MSH2 is one of two proteins, now designated MSH3 and MSH6.