Werner Syndrome (WS) is an autosomal recessive condition characterized by an early onset of age-related symptoms. WS patients also experience an increased risk of rare non-epithelial cancers, especially mesenchymalneoplasms such as sarcomas. Fibroblasts isolated from WS cells senesce prematurely in culture and display increased chromosomal aberrations. WRN, the protein mutated in WS, is unique among the RecQ family proteins possesses on exonuclease activity and 32 to 52 helicase in a single polypeptide. There is accumulating evidence suggesting that WRN contributes to the maintenance of genomic integrity through its involvement in various DNA damage repair pathways and plays a role in telomere maintenance. However, the mechanism by which WRN functions in DNA repair, especially in DNA double-strand break (DSB) repair is still elusive. In vitro and indirect evidence leads to the conclusion that WRN may play a role both in homologous recombination (HR) as well as nonhomologous end joining (NHEJ). Recently, evidence showed that WRN is recruited to DNA damage sites and phosphorylated by PIKK3 kinase family in response to DNA DSB. In this proposal, we will test the hypothesis that WRN is recruited to DNA double-strand breaks (DSB) in vivo, to determine the function of WRN phosphorylation, and its involvement in the process of NHEJ or HR in response to DNA damage.
Our specific aims are: (1) To determine the mechanism by which WRN is recruited to the sites of DNA double-strand breaks;(2) To test the hypothesis that WRN is phosphorylated by DNA-PK in response to DNA double-strand breaks and the phosphorylation status of WRN modulates its functions at DNA damage sites;and (3) To verify the hypothesis that WRN plays a role in nonhomologous end joining (NHEJ) and/or homologous recombination (HR) pathways of DNA double-strand break repair. Accomplishment of the proposed research would lead to the understanding of WRN's function in response to DNA damage and help further elucidate the role of WRN in cancer.
Werner Syndrome (WS) is an autosomal recessive condition characterized by an early onset of age-related symptoms. WS patients also experience an increased risk of rare non-epithelial cancers, especially mesenchymal neoplasms such as sarcomas. WRN, the protein defective in WS is involved in maintenance of genomic integrity and DNA damage repair. To understand the function of WRN in DNA damage response, we proposed to (i) determine the mechanism by which WRN is recruited to the sites of DNA damage in vivo, (ii) find out kinases that are responsible for WRN phosphorylation and (iii) determine the biological significance of WRN phosphorylation in the process of DNA double strand break repair mediated through non- homologous end joining and/or homologous recombination. The results obtained with these experiments will further elucidate the mechanism by which WRN contributes in genome maintenance, cancer and DNA repair.
|Lee, Kyung-Jong; Saha, Janapriya; Sun, Jingxin et al. (2016) Phosphorylation of Ku dictates DNA double-strand break (DSB) repair pathway choice in S phase. Nucleic Acids Res 44:1732-45|
|Su, Fengtao; Mukherjee, Shibani; Yang, Yanyong et al. (2014) Nonenzymatic role for WRN in preserving nascent DNA strands after replication stress. Cell Rep 9:1387-401|
|Davis, Anthony J; Chi, Linfeng; So, Sairei et al. (2014) BRCA1 modulates the autophosphorylation status of DNA-PKcs in S phase of the cell cycle. Nucleic Acids Res 42:11487-501|
|Davis, Anthony J; Chen, Benjamin P C; Chen, David J (2014) DNA-PK: a dynamic enzyme in a versatile DSB repair pathway. DNA Repair (Amst) 17:21-9|
|Davis, Anthony J; Lee, Kyung-Jong; Chen, David J (2013) The N-terminal region of the DNA-dependent protein kinase catalytic subunit is required for its DNA double-stranded break-mediated activation. J Biol Chem 288:7037-46|
|Sun, Jingxin; Lee, Kyung-Jong; Davis, Anthony J et al. (2012) Human Ku70/80 protein blocks exonuclease 1-mediated DNA resection in the presence of human Mre11 or Mre11/Rad50 protein complex. J Biol Chem 287:4936-45|
|Shao, Zhengping; Davis, Anthony J; Fattah, Kazi R et al. (2012) Persistently bound Ku at DNA ends attenuates DNA end resection and homologous recombination. DNA Repair (Amst) 11:310-6|
|Richard, Derek J; Savage, Kienan; Bolderson, Emma et al. (2011) hSSB1 rapidly binds at the sites of DNA double-strand breaks and is required for the efficient recruitment of the MRN complex. Nucleic Acids Res 39:1692-702|
|Castore, Reneau; Hughes, Cameron; Debeaux, Austin et al. (2011) Mycobacterium tuberculosis Ku can bind to nuclear DNA damage and sensitize mammalian cells to bleomycin sulfate. Mutagenesis 26:795-803|
|Asaithamby, Aroumougame; Chen, David J (2011) Mechanism of cluster DNA damage repair in response to high-atomic number and energy particles radiation. Mutat Res 711:87-99|
Showing the most recent 10 out of 16 publications