title: The mammalian mismatch repair protein MSH2 is required for correct MRE11 and RAD51 relocalization and for efficient cell cycle arrest induced by ionizing radiation in G2 phase.
abstract: In yeast, MSH2 plays an important role in mismatch repair (MMR) and recombination, whereas the function of the mammalian MSH2 protein in recombinational repair is not completely established. We examined the cellular responses of MSH2-deficient mouse cells to X-rays to clarify the role of MSH2 in recombinational repair. Cell survival, checkpoint functions and relocalization of the recombination-related proteins MRE11 and RAD51 were analysed in embryonic fibroblasts derived from MSH2(+/+) and MSH2(-/-) mice, and in MSH2-proficient and deficient mouse colorectal carcinoma cells. Loss of MSH2 function was found to be associated with reduction in cell survival following radiation, absence of either MRE11 or RAD51 relocalization and a higher level of X-ray-induced chromosomal damage specifically in G2-phase cells. Finally, MSH2(-/-) cells showed an inefficient early G2/M checkpoint, being arrested only transiently after irradiation before progressing into mitosis. Consistent with the premature release from the G2-phase arrest, activation of CHK1 was transient and CHK2 was not phosphorylated in synchronized MSH2-null cells. Our data suggest that an active MSH2 is required for a correct response to ionizing radiation-induced DNA damage in the G2 phase of the cell cycle, possibly connecting DSB repair to checkpoint signalling.
authors.affiliation: Laboratorio di Citogenetica Molecolare e Mutagenesi-DABAC, Università delgi Studi della Tuscia, Via S, Camillo de Lellis, Viterbo, Italy.
authors.forename: Annapaola
authors.initials: A
authors.lastname: Franchitto
authors.forename: Pietro
authors.initials: P
authors.lastname: Pichierri
authors.forename: Rita
authors.initials: R
authors.lastname: Piergentili
authors.forename: Marco
authors.initials: M
authors.lastname: Crescenzi
authors.forename: Margherita
authors.initials: M
authors.lastname: Bignami
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Palitti
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D002842:Chromatids / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects*; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000494:pharmacology; D016195:G2 Phase; D000076228:MRE11 Homologue Protein; D051379:Mice; D051718:MutS Homolog 2 Protein; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051135:Rad51 Recombinase
chemical_list: D004268:DNA-Binding Proteins; C512689:Mre11a protein, mouse; D011518:Proto-Oncogene Proteins; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; D000076228:MRE11 Homologue Protein; C497173:Msh2 protein, mouse; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes