biostudies-literatureKedar PSIntramural NIH HHS360-8https://www.ebi.ac.uk/biostudies/studies/S-EPMC3307909biostudies-literatureUnknown10(3)Treatment of base excision repair-proficient mouse fibroblasts with the DNA alkylating agent methyl methanesulfonate (MMS) and a small molecule inhibitor of PARP-1 results in a striking cell killing phenotype, as previously reported. Earlier studies showed that the mechanism of cell death is apoptosis and requires DNA replication, expression of PARP-1, and an intact S-phase checkpoint cell signaling system. It is proposed that activity-inhibited PARP-1 becomes immobilized at DNA repair intermediates, and that this blocks DNA repair and interferes with DNA replication, eventually promoting an S-phase checkpoint and G(2)-M block. Here we report studies designed to evaluate the prediction that inhibited PARP-1 remains DNA associated in cells undergoing repair of alkylation-induced damage. Using chromatin immunoprecipitation with anti-PARP-1 antibody and qPCR for DNA quantification, a higher level of DNA was found associated with PARP-1 in cells treated with MMS plus PARP inhibitor than in cells without inhibitor treatment. These results have implications for explaining the extreme hypersensitivity phenotype after combination treatment with MMS and a PARP inhibitor.Molecular cancer research : MCRIncreased PARP-1 association with DNA in alkylation damaged, PARP-inhibited mouse fibroblasts.PMC3307909Z01 ES050159-11Z01 ES050159Horton JKKedar PSWilson SHStefanick DFfalseIncreased PARP-1 association with DNA in alkylation damaged, PARP-inhibited mouse fibroblasts.Treatment of base excision repair-proficient mouse fibroblasts with the DNA alkylating agent methyl methanesulfonate (MMS) and a small molecule inhibitor of PARP-1 results in a striking cell killing phenotype, as previously reported. Earlier studies showed that the mechanism of cell death is apoptosis and requires DNA replication, expression of PARP-1, and an intact S-phase checkpoint cell signaling system. It is proposed that activity-inhibited PARP-1 becomes immobilized at DNA repair intermediates, and that this blocks DNA repair and interferes with DNA replication, eventually promoting an S-phase checkpoint and G(2)-M block. Here we report studies designed to evaluate the prediction that inhibited PARP-1 remains DNA associated in cells undergoing repair of alkylation-induced damage. Using chromatin immunoprecipitation with anti-PARP-1 antibody and qPCR for DNA quantification, a higher level of DNA was found associated with PARP-1 in cells treated with MMS plus PARP inhibitor than in cells without inhibitor treatment. These results have implications for explaining the extreme hypersensitivity phenotype after combination treatment with MMS and a PARP inhibitor.2012-01-01T00:00:00Z2012 Mar2024-11-14T10:44:50.968Z2019-06-05T17:09:43ZS-EPMC33079092224623710.1158/1541-7786.mcr-11-047710.1158/1541-7786.MCR-11-0477