title: DNA mismatch repair-dependent response to fluoropyrimidine-generated damage.
abstract: Previous studies from our laboratory indicated that expression of the MLH1 DNA mismatch repair (MMR) gene was necessary to restore cytotoxicity and an efficient G(2) arrest in HCT116 human colon cancer cells, as well as Mlh1(-/-) murine embryonic fibroblasts, after treatment with 5-fluoro-2'-deoxyuridine (FdUrd). Here, we show that an identical phenomenon occurred when expression of MSH2, the other major MMR gene, was restored in HEC59 human endometrial carcinoma cells or was present in adenovirus E1A-immortalized Msh2(+/+) (compared with isogenic Msh2(-/-)) murine embryonic stem cells. Because MMR status had little effect on cellular responses (i.e. G(2) arrest and lethality) to the thymidylate synthase inhibitor, Tomudex, and a greater level of [(3)H]FdUrd incorporation into DNA was found in MMR-deficient cells, we concluded that the differential FdUrd cytotoxicity between MMR-competent and MMR-deficient cells was mediated at the level of DNA incorporation. Analyses of ATPase activation suggested that the hMSH2-hMSH6 heterodimer only recognized FdUrd moieties (as the base 5-fluorouracil (FU) in DNA) when mispaired with guanine, but not paired with adenine. Furthermore, analyses of incorporated FdUrd using methyl-CpG-binding domain 4 glycosylase indicated that there was more misincorporated FU:Gua in the DNA of MMR-deficient HCT116 cells. Our data provide the first demonstration that MMR specifically detects FU:Gua (in the first round of DNA replication), signaling a sustained G(2) arrest and lethality.
authors.affiliation: Department of Radiation Oncology and Case Comprehensive Cancer Center, Laboratory of Molecular Stress Responses, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Meyers
authors.forename: Mark W
authors.initials: MW
authors.lastname: Wagner
authors.forename: Anthony
authors.initials: A
authors.lastname: Mazurek
authors.forename: Christoph
authors.initials: C
authors.lastname: Schmutte
authors.forename: Richard
authors.initials: R
authors.lastname: Fishel
authors.forename: David A
authors.initials: DA
authors.lastname: Boothman
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D020137:Base Pair Mismatch / Q000235:genetics*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects*; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C078444:MSH3 protein, human; D000074081:MutS Homolog 3 Protein; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; D011799:Quinazolines; D013876:Thiophenes; C029269:5-fluoropyrimidine; D004247:DNA; D000251:Adenosine Triphosphatases; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein; C068874:raltitrexed