title: MutS inhibits RecA-mediated strand exchange with platinated DNA substrates.
abstract: Human cell lines and Escherichia coli dam mutants are sensitive to the cytotoxic action of the anticancer agent, cisplatin. Introduction of mutations disabling DNA mismatch repair into these cell lines renders them resistant to the action of this drug. We used RecA-mediated strand exchange between homologous phiX174 molecules, one that was platinated and the other that was unmodified, to show that strand transfer is decreased in a dose-dependent manner. Transfer was severely decreased at 10 adducts per molecule (5,386 bp) and abolished with 24 adducts. At low levels of adduction, addition of MutS to the reaction further decreases the rate and yield in a dose-dependent manner. MutL addition was without effect even in the presence of MutS. The results suggest that although mismatch repair is beneficial for mutation avoidance, its antirecombination activity on inappropriate substrates can be lethal to the cell.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Calmann
authors.forename: M G
authors.initials: MG
authors.lastname: Marinus
mesh_terms: D000251:Adenosine Triphosphatases / Q000502:physiology*; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001426:Bacterial Proteins / Q000502:physiology*; D020137:Base Pair Mismatch; D002470:Cell Survival / Q000235:genetics; D002945:Cisplatin / Q000378:metabolism* / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism*; D004260:DNA Repair / Q000502:physiology; D045643:DNA Repair Enzymes / Q000502:physiology; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000502:physiology; D051719:MutS DNA Mismatch-Binding Protein; D009690:Nucleic Acid Conformation; D011938:Rec A Recombinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011995:Recombination, Genetic / Q000235:genetics; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D001426:Bacterial Proteins; D018736:DNA Adducts; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C057270:cisplatin-DNA adduct; D004247:DNA; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D011938:Rec A Recombinases; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli; D045643:DNA Repair Enzymes; D002945:Cisplatin