DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB r...DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB repair plays dominant roles in safeguarding oocyte quantity and quality. However, little is known regarding the key players of the HR repair pathway in oocytes. Here, we identified oocyte-specific gene Ooep as a novel key component of the HR repair pathway in mouse oocytes. OOEP was required for efficient ataxia telangiectasia mutated （ATM） kinase activation and Rad51 recombinase （RAD51） focal accumulation at DNA DSBs. Ooep null oocytes were defective in DNA DSB repair and prone to apoptosis upon exogenous DNA damage insults. Moreover, Ooep null oocytes exhibited delayed meiotic maturation. Therefore, OOEP played roles in preserving oocyte quantity and quality by maintaining genome stability. Ooep expression decreased with the advance of maternal age, suggesting its involvement in maternal aging.展开更多
It is proposed that mismatch repair (MMR) mediates the cytotoxic effects of DNA damaging agents by exerting a futile repair pathway which leads to double strand breaks (DSBs). Previous reports indicate that the sensit...It is proposed that mismatch repair (MMR) mediates the cytotoxic effects of DNA damaging agents by exerting a futile repair pathway which leads to double strand breaks (DSBs). Previous reports indicate that the sensitivity of cells defective in homologous recombination (HR) to DNA alkylation is reduced by defects in MMR genes. We have assessed the contribution of different MMR genes to the processing of alkylation damage in vivo. We have directly visualized recombination complexes formed upon DNA damage using fluorescent protein (FP) fusions. We find that msh6 mutants are more resistant than wild type cells to MNNG, and that an msh6 mutation rescues the sensitivity of rad52 strains more efficiently than an msh3 mutation. Analysis of RAD52-GFP tagged strains indicate that MNNG increases repair foci formation, and that the inactivation of the MHS2 and MSH6 genes but not the MSH3 gene result in a reduction of the number of foci formed. In addition, in the absence of HR, NHEJ could process the MNNG-induced DSBs as indicated by the formation of NHEJ-GFP tagged foci. These data suggest that processing of the alkylation damage by MMR, mainly by MSH2-MSH6, is required for recruitment of recombination proteins to the damage site for repair.展开更多
Genomic instability is a characteristic of cancer cells.In order to maintain genomic integrity,cells have evolved a complex DNA repair system to detect,signal and repair a diversity of DNA lesions.Homologous recombina...Genomic instability is a characteristic of cancer cells.In order to maintain genomic integrity,cells have evolved a complex DNA repair system to detect,signal and repair a diversity of DNA lesions.Homologous recombination(HR)-mediated DNA repair represents an error-free repair mechanism to maintain genomic integrity and ensure high-fidelity transmission of genetic information.Deficiencies in HR repair are of tremendous importance in the etiology of human cancers and at the same time offer great opportunities for designing targeted therapeutic strategies.The increase in the number of proteins identified as being involved in HR repair has dramatically shifted our concept of the proteins involved in this process:traditionally viewed as existing in a linear and simple pathway,today they are viewed as existing in a dynamic and interconnected network.Moreover,exploration of the targets within this network that can be modulated by small molecule drugs has led to the discovery of many effective kinase inhibitors,such as ATM,ATR,DNA-PK,CHK1,and CHK2 inhibitors.In preclinical studies,these inhibitors have been shown to sensitize cancer cells to chemotherapy and radiation therapy.The most exciting discovery in the field of HR repair is the identification of the synthetic lethality relationship between poly(ADPribose)polymerase(PARP)inhibitors and HR deficiency.The promises of clinical applications of PARP inhibitors and the concept of synthetic lethality also bring challenges into focus.Future research directions in the area of HR repair include determining how to identify the patients most likely to benefit from PARP inhibitors and developing strategies to overcome resistance to PARP inhibitors.展开更多
基金supported by the National Key Research and Development Program of China(2017YFC1001102)National Natural Science Foundation of China(81760507)
文摘DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB repair plays dominant roles in safeguarding oocyte quantity and quality. However, little is known regarding the key players of the HR repair pathway in oocytes. Here, we identified oocyte-specific gene Ooep as a novel key component of the HR repair pathway in mouse oocytes. OOEP was required for efficient ataxia telangiectasia mutated （ATM） kinase activation and Rad51 recombinase （RAD51） focal accumulation at DNA DSBs. Ooep null oocytes were defective in DNA DSB repair and prone to apoptosis upon exogenous DNA damage insults. Moreover, Ooep null oocytes exhibited delayed meiotic maturation. Therefore, OOEP played roles in preserving oocyte quantity and quality by maintaining genome stability. Ooep expression decreased with the advance of maternal age, suggesting its involvement in maternal aging.
文摘It is proposed that mismatch repair (MMR) mediates the cytotoxic effects of DNA damaging agents by exerting a futile repair pathway which leads to double strand breaks (DSBs). Previous reports indicate that the sensitivity of cells defective in homologous recombination (HR) to DNA alkylation is reduced by defects in MMR genes. We have assessed the contribution of different MMR genes to the processing of alkylation damage in vivo. We have directly visualized recombination complexes formed upon DNA damage using fluorescent protein (FP) fusions. We find that msh6 mutants are more resistant than wild type cells to MNNG, and that an msh6 mutation rescues the sensitivity of rad52 strains more efficiently than an msh3 mutation. Analysis of RAD52-GFP tagged strains indicate that MNNG increases repair foci formation, and that the inactivation of the MHS2 and MSH6 genes but not the MSH3 gene result in a reduction of the number of foci formed. In addition, in the absence of HR, NHEJ could process the MNNG-induced DSBs as indicated by the formation of NHEJ-GFP tagged foci. These data suggest that processing of the alkylation damage by MMR, mainly by MSH2-MSH6, is required for recruitment of recombination proteins to the damage site for repair.
基金The authors thank Alexandra Surcel and Carey L Hendrix Lord for helpful comments on this manuscript.The work in our laboratory is supported by grants from the National Science Foundation(IBN-0077832,MCB-9896340,MCB-0092075)the National Institutes of Health(R0 1 GM63871)+3 种基金the US Department of Agriculture(2001-35301-10570 and 2003-35301-13313)Wuxing L was partially supported by the Intercollege Graduate Degree Program in Plant PhysiologyHong M gratefully acknowledges the support of the John Simon Guggenheim Foundationthe National Institutes of Health(F33 GM72245-1).
文摘Genomic instability is a characteristic of cancer cells.In order to maintain genomic integrity,cells have evolved a complex DNA repair system to detect,signal and repair a diversity of DNA lesions.Homologous recombination(HR)-mediated DNA repair represents an error-free repair mechanism to maintain genomic integrity and ensure high-fidelity transmission of genetic information.Deficiencies in HR repair are of tremendous importance in the etiology of human cancers and at the same time offer great opportunities for designing targeted therapeutic strategies.The increase in the number of proteins identified as being involved in HR repair has dramatically shifted our concept of the proteins involved in this process:traditionally viewed as existing in a linear and simple pathway,today they are viewed as existing in a dynamic and interconnected network.Moreover,exploration of the targets within this network that can be modulated by small molecule drugs has led to the discovery of many effective kinase inhibitors,such as ATM,ATR,DNA-PK,CHK1,and CHK2 inhibitors.In preclinical studies,these inhibitors have been shown to sensitize cancer cells to chemotherapy and radiation therapy.The most exciting discovery in the field of HR repair is the identification of the synthetic lethality relationship between poly(ADPribose)polymerase(PARP)inhibitors and HR deficiency.The promises of clinical applications of PARP inhibitors and the concept of synthetic lethality also bring challenges into focus.Future research directions in the area of HR repair include determining how to identify the patients most likely to benefit from PARP inhibitors and developing strategies to overcome resistance to PARP inhibitors.
