title: Efficient repair of A/C mismatches in mouse cells deficient in long-patch mismatch repair.
abstract: A previously unrecognized mismatch repair activity is described. Extracts of immortalized MSH2-deficient mouse fibroblasts did not correct most single base mispairs. The same extracts carried out efficient repair of A/C mismatches. A/G mispairs were less efficiently corrected and there was no significant repair of A/A. MLH1-defective mouse extracts also repaired an A/C mispair. A/C correction by Msh2(-/-) mouse cell extracts was not affected by antibodies against the PMS2 protein, which inhibited long-patch mismatch repair. A/C repair activity is thus independent of MutSalpha, MutSbeta and MutLalpha. A/C mismatches were corrected 5-fold more efficiently by extracts of Msh2 knockout mouse cells than by comparable extracts prepared from hMSH2- or hMLH1-deficient human cells. MSH2-independent A/C correction by mouse cell extracts did not require a nick in the circular duplex DNA substrate. Repair involved replacement of the A and was associated with the resynthesis of a limited stretch of </=25 bases of DNA.
authors.affiliation: Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK.
authors.forename: S
authors.initials: S
authors.lastname: Oda
authors.forename: O
authors.initials: O
authors.lastname: Humbert
authors.forename: S
authors.initials: S
authors.lastname: Fiumicino
authors.forename: M
authors.initials: M
authors.lastname: Bignami
authors.forename: P
authors.initials: P
authors.lastname: Karran
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D020137:Base Pair Mismatch; D001483:Base Sequence; D002352:Carrier Proteins; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004260:DNA Repair; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; C497173:Msh2 protein, mouse; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein