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 À/À 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 À/À 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.

Reply to “Is mismatch repair really required for ionizing radiation–induced DNA damage signaling?”

“…But it may be premature to conclude that MMR does not have any role in ionizing radiation-induced DNA damage signaling. For example, Franchitto et al 2 reported that Msh2 was required to sustain G2 arrest in response to ionizing radiation, a finding that is in agreement with studies conducted on MMR-deficient human tumor lines 4,5 . Furthermore, Zeng et al 6 showed that Pms2-deficient MEFs had significantly less apoptosis after irradiation than wild-type MEFs, and similar results were obtained in a study that examined Msh2-deficient mouse embryonic stem cells 7 .…”

Multiple roles for MSH2 in the repair of a deletion mutation directed by modified single-stranded oligonucleotides

“…MMR proteins have also been shown to inhibit recombination between divergent DNA sequences and are responsible for maintenance of the G2 checkpoint by CHK2 following DNA damage (Chen and Jinks-Robertson, 1999;Datta et al, 1996;Franchitto et al, 2003;Selva et al, 1995). MSH2 interacts directly with HR proteins (Brown et al, 2003;Wang et al, 2000), some of which have now been shown to play a direct role in the TNE process .…”

TRIM29 regulates the assembly of DNA repair proteins into damaged chromatin

“…Among these DNA repair proteins, TRIM29 directly binds to MSH2. It has been reported that MMR proteins including MSH2 function as molecular scaffolds to regulate ATM activity and regulate the recruitment of MRE11 to DSB sites 39,40 . Consistent with these findings, we revealed that TRIM29 forms a scaffold structure with DNA MMR proteins on chromatin to regulate DNA damage signalling.…”