title: Mismatch repair protein hMSH2-hMSH6 recognizes mismatches and forms sliding clamps within a D-loop recombination intermediate.
abstract: High fidelity homologous DNA recombination depends on mismatch repair (MMR), which antagonizes recombination between divergent sequences by rejecting heteroduplex DNA containing excessive nucleotide mismatches. The hMSH2-hMSH6 heterodimer is the first responder in postreplicative MMR and also plays a prominent role in heteroduplex rejection. Whether a similar molecular mechanism underlies its function in these two processes remains enigmatic. We have determined that hMSH2-hMSH6 efficiently recognizes mismatches within a D-loop recombination initiation intermediate. Mismatch recognition by hMSH2-hMSH6 is not abrogated by human replication protein A (HsRPA) bound to the displaced single-stranded DNA (ssDNA) or by HsRAD51. In addition, ATP-bound hMSH2-hMSH6 sliding clamps that are essential for downstream MMR processes are formed and constrained within the heteroduplex region of the D-loop. Moreover, the hMSH2-hMSH6 sliding clamps are stabilized on the D-loop by HsRPA bound to the displaced ssDNA. Our findings reveal similarities and differences in hMSH2-hMSH6 mismatch recognition and sliding-clamp formation between a D-loop recombination intermediate and linear duplex DNA.
authors.affiliation: Department of Biochemistry, University of Iowa, Iowa City, IA 52242.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Honda
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okuno
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Hengel
authors.forename: Juana V
authors.initials: JV
authors.lastname: Martín-López
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cook
authors.forename: Ravindra
authors.initials: R
authors.lastname: Amunugama
authors.forename: Randal J
authors.initials: RJ
authors.lastname: Soukup
authors.forename: Shyamal
authors.initials: S
authors.lastname: Subramanyam
authors.forename: Richard
authors.initials: R
authors.lastname: Fishel
authors.forename: Maria
authors.initials: M
authors.lastname: Spies
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D020137:Base Pair Mismatch; D019921:Biotinylation; D004247:DNA / Q000737:chemistry*; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D051718:MutS Homolog 2 Protein / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051135:Rad51 Recombinase / Q000737:chemistry; D011995:Recombination, Genetic; D051716:Replication Protein A / Q000737:chemistry
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C497167:RPA1 protein, human; D051716:Replication Protein A; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D004247:DNA; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein
keywords: homeologous recombination; homologous recombination; mismatch DNA repair; single-molecule; total internal reflection fluorescence microscopy