Deficiencies in DNA-damage signaling and repair pathways are fundamental to the etiology of most human cancers. Of the many types of DNA damage that occur within the cell, DNA double-strand breaks (DSBs) are particularly dangerous. DSBs are caused by both endogenous and exogenous threats, including ionizing radiation (IR). An inability to respond properly to DSBs or to repair them correctly can lead to mutation, genome instability, cell death and tumorigenesis. Our research is focused on the mechanisms by which cells recognize, respond to, and repair of Ionizing radiation induced DSBs. We are motivated by the fact that a more complete understanding of these pathways will provide insights into how cancer is triggered, and may lead to the development of more effective cancer therapies.
Eukaryotic cells have evolved two distinct mechanisms for repairing DSBs: homologous recombination (HR) and non-homologous end joining (NHEJ). These mechanisms differ primarily in that HR requires a homologous DNA template, while NHEJ acts independently of homologous DNA. The DNA dependent protein kinase (DNA-PK) complex, consisting of the DNA-binding subunit Ku and the catalytic subunit DNA-PKcs, are central to NHEJ repair. Utilizing transgenic mouse models, we have demonstrated that the kinase activity of DNA-PKcs is essential for the repair of DNA DSBs. Recently, we have also demonstrated that DNA-PKcs is autophosphorylated and phosphorylated by ATM in response to IR. Utilizing live cell imaging combined with localized UV-A micro point laser irradiation, we have showed that DNA-PKcs and Ku are recruited to DNA damage sites within seconds after laser damage. Combining genetic manipulation, laser irradiation and live cell imaging, we will be able to establish a temporal relationship among the various factors in the NHEJ pathway. In addition to study the kinetics and temporal spatial relationship of the recruitment of the repair factors, we also utilize FRAP analysis to understand the dynamics of the repair proteins at the DNA damage sites. Further more, we are establishing single molecular approach to understand the dynamics of repair proteins in response to DNA damage at single molecular level.
A cell’s ability to repair damaged DNA is critical, not only for the prevention of malignancy, but also for the resistance of many tumors to current therapies. Understanding DNA repair processes and cellular radiation responses in general will therefore help to improve the efficiency of radiation treatment and to protect the normal tissues during radiation therapy. In this respect, we are also interested in studying radiation responses in tumor and normal cells with the objective to improve radiation therapy and cancer treatment in general.
RESEARCH INTERESTS
The role of DNA-PK in DNA double-strand break repair
Structural Cell Biology of DNA Repair Machines
DNA damage responses induced by HZE particles in human cells
RECENT PUBLICATIONS
Chen BP, Chan DW, Kobayashi J, Burma S, Asaithamby A, Morotomi-Yano K, Botvinick E, Qin J, Chen DJ, "Cell cycle dependence of DNA-dependent protein kinase phosphorylation in response to DNA double strand breaks" J Biol Chem, 280:14709-15, 2005
Perry JJ, Yannone SM, Holden LG, Hitomi C, Asaithamby A, Han S, Cooper PK, Chen DJ, Tainer JA, "WRN exonuclease structure and molecular mechanism imply an editing role in DNA end processing" Nat Struct Mol Biol, 13:414-22, 2006
Burma S, Chen BP, Chen DJ, "Role of non-homologous end joining (NHEJ) in maintaining genomic integrity" DNA Repair, 5:1042-8, 2006
Chen BP, Uematsu N, Kobayashi J, Lerenthal Y, Krempler A, Yajima H, Lobrich M, Shiloh Y, Chen DJ, "Ataxia telangiectasia mutated (ATM) is essential for DNA-PKcs phosphorylations at the Thr-2609 cluster upon DNA double strand break" J Biol Chem, 282:6582-7, 2007
48. Yano K, Morotomi-Yano K, Wang SY, Uematsu N, Lee KJ, "Ku recruits XLF to DNA double-strand breaks" EMBO, 9:91-6, 2008
SIGNIFICANT PUBLICATIONS
Yannone SM, Roy S, Chan DW, Murphy MB, Huang S, Campisi J, Chen DJ, "Werner syndrome protein is regulated and phosphorylated by DNA-dependent" J Biol Chem., 276:38242-8, 2001
Chan DW, Chen BP, Prithivirajsingh S, Kurimasa A, Story MD, Qin J, Chen DJ, "Autophosphorylation of the DNA-dependent protein kinase catalytic subunit is" Genes Dev, 16:2333-8, 2002
Uematsu N, Weterings E, Yano K, Morotomi-Yano K, Jakob B, Taucher-Scholz G, Mari PO, van Gent DC, Chen BP, Chen DJ, "Autophosphorylation of DNA-PKCS regulates its dynamics at DNA double-strand breaks" J Cell Biol, 177:219-29, 2007
47. Weterings E, Chen DJ., "The endless tale of non-homologous end-joining" Cell Research, 18:114-24, 2008
51. Yano KI, Chen DJ, "Live cell imaging of XLF and XRCC4 reveals a novel view of protein assembly in the non-homologous end-joining pathway." Cell Cycle, 7:1321-5
Point and right click (click and hold for Mac users) your mouse onand select "Save this link (or target) as..." option to save the file to your local computer.
and select "Save this link (or target) as..." option to save the file to your local computer.