5′->3′ double-stranded DNA exonuclease which may also possess a cryptic 3′->5′ double-stranded DNA exonuclease activity. Functions in DNA mismatch repair (MMR) to excise mismatch-containing DNA tracts directed by strand breaks located either 5′ or 3′ to the mismatch. Also exhibits endonuclease activity against 5′-overhanging flap structures similar to those generated by displacement synthesis when DNA polymerase encounters the 5′-end of a downstream Okazaki fragment. Required for somatic hypermutation (SHM) and class switch recombination (CSR) of immunoglobulin genes. Essential for male and female meiosis.
