Exonuclease 1, hExo1, 31--, Exonuclease I, hExoI, EXO1, EXOI, HEX1
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.