Interaction of proliferating cell nuclear antigen with PMS2 is required for MutLa activation and function in mismatch repair

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 114; no. 19; p. 4930
• Main Authors: Genschel, Jochen, Kadyrova, Lyudmila Y, Iyer, Ravi R, Dahal, Basanta K, Kadyrov, Farid A, Modrich, Paul
• Format: Journal Article
• Language: English
• Published: Washington National Academy of Sciences 09-05-2017
• Subjects: Activation; Adenosine triphosphatase; Amino acid substitution; Amino acids; Antigens; Deoxyribonucleic acid; DNA; Endonuclease; Eukaryotes; Genotype & phenotype; In vitro methods and tests; Mismatch repair; MLH1 protein; Mutation; Proliferating cell nuclear antigen; Repair; Yeast
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1702561114

Eukaryotic MutLa (mammalian MLH1-PMS2 heterodimer; MLH1-PMS1 in yeast) functions in early steps of mismatch repair as a latent endonuclease that requires a mismatch, MutSa/β, and DNA-loaded proliferating cell nuclear antigen (PCNA) for activation. We show here that human PCNA and MutLa interact specifically but weakly in solution to form a complex of approximately 1:1 stoichiometry that depends on PCNA interaction with the C-terminal endonuclease domain of the MutLa PMS2 subunit. Amino acid substitution mutations within a PMS2 C-terminal ^sup 721^QRLIAP motif attenuate or abolish human MutLa interaction with PCNA, as well as PCNA-dependent activation of MutLa endonuclease, PCNA- and DNA-dependent activation of MutLa ATPase, and MutLa function in in vitro mismatch repair. Amino acid substitution mutations within the corresponding yeast PMS1 motif (^sup 723^QKLIIP) reduce or abolish mismatch repair in vivo. Coupling of a weak allele within this motif (^sup 723^AKLIIP) with an exo1Δ null mutation, which individually confer only weak mutator phenotypes, inactivates mismatch repair in the yeast cell.