Exonuclease 1 (EXO1)

Exonuclease 1 is a protein with 5""" to 3""" exonuclease activity as well as an RNase H activity. It is similar to the Saccharomyces cerevisiae protein Exo1 which interacts with Msh2 and which is involved in mismatch repair and recombination. Alternative splicing of this gene results in three transcript variants encoding two different isoforms.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.