title: Apoptosis and mutation in the murine small intestine: loss of Mlh1- and Pms2-dependent apoptosis leads to increased mutation in vivo.
abstract: The mismatch repair (MMR) protein Msh2 has been shown to function in the apoptotic response to alkylating agents in vivo. Here, we extend these studies to the MutL homologues (MLH) Mlh1 and Pms2 by analysing the apoptotic response within the small intestine of gene targeted strains. We demonstrate significant differences between Msh2, Mlh1 and Pms2 mutations in influencing apoptotic signalling following 50mg/kg N-methyl-nitrosourea (NMNU), with no obvious reliance upon either Mlh1 or Pms2. However, following exposure to 100mg/kg temozolomide or lower levels of NMNU (10mg/kg) both Mlh1- and Pms2-dependent apoptosis was observed, indicating that the apoptotic response at these levels of DNA damage is dependent on the MutL homologues. Given our ability to observe a MutLalpha dependence of the apoptotic response, we tested whether perturbations of this response directly translate into increases in mutation frequency in vivo. We show that treatment with temozolomide or 10mg/kg NMNU significantly increases mutation in both the Mlh1 and Pms2 mutant mice. At higher levels of NMNU, where the apoptotic response is independent of Mlh1 and Pms2, no gene dependent increase in mutation frequency was observed. These results argue that the MutSalpha and MutLalpha are not equally important in their ability to signal apoptosis. However, when MMR does mediate apoptosis, perturbation of this response leads to long-term persistence of mutant cells in vivo.
authors.affiliation: School of Biosciences, University of Cardiff, Museum Avenue, P.O. Box 911, Cardiff, Wales CF10 3US, UK.
authors.forename: Owen J
authors.initials: OJ
authors.lastname: Sansom
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Bishop
authors.forename: Helen
authors.initials: H
authors.lastname: Court
authors.forename: Sandra
authors.initials: S
authors.lastname: Dudley
authors.forename: R Michael
authors.initials: RM
authors.lastname: Liskay
authors.forename: Alan R
authors.initials: AR
authors.lastname: Clarke
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D020137:Base Pair Mismatch; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002352:Carrier Proteins; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008770:Methylnitrosourea / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D008817:Mice, Mutant Strains; D000070976:Mismatch Repair Endonuclease PMS2; D008940:Mitotic Index; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D000077204:Temozolomide; D013997:Time Factors
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D008770:Methylnitrosourea; D003606:Dacarbazine; D000251:Adenosine Triphosphatases; C499533:Pms2 protein, mouse; D000070976:Mismatch Repair Endonuclease PMS2; C497173:Msh2 protein, mouse; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes; D001973:Bromodeoxyuridine; D000077204:Temozolomide