The Saccharomyces cerevisiae Msh2 mismatch repair protein localizes to recombination intermediates in vivo

Mismatch repair proteins act during double-strand break repair (DSBR) to co rrect mismatches in heteroduplex DNA, to suppress recombination between div ergent sequences, and to promote removal of nonhomologous DNA at DSB ends. We investigated yeast Msh2p association with recombination intermediates in vivo using chromatin immunoprecipitation. During DSBR involving nonhomolog ous ends, Msh2p localized strongly to recipient and donor sequences. Locali zation required Msh3p and was greatly reduced in rad50 Delta strains. Minim al localization of Msh2p was observed during fully homologous repair, but t his was increased in rad52 Delta strains. These findings argue that Msh2p-M sh3p associates with intermediates early in DSBR to participate in the reje ction of homeologous pairing and to stabilize nonhomologous tails for cleav age by Rad1p-Rad10p endonuclease.