TNKS1BP1 functions in DNA double-strand break repair though facilitating DNA-PKcs autophosphorylation dependent on PARP-1

// Lian-Hong Zou 1, 2 , Zeng-Fu Shang 2, 3 , Wei Tan 1, 2 , Xiao-Dan Liu 2 , Qin-Zhi Xu 2 , Man Song 2, 3 , Yu Wang 2 , Hua Guan 2 , Shi-Meng Zhang 2 , Lan Yu 4 , Cai-Gao Zhong 1 , Ping-Kun Zhou 2, 3 1 School of Public Heath, Central South University, Changsha, Hunan Province 410078, P. R. China 2 Department of Radiation Toxicology and Oncology, Beijing Key Laboratory for Radiobiology, Beijing Institute of Radiation Medicine, Beijing 100850, P. R. China 3 School of Radiation Medicine and Protection, Medical College of Soochow University, Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Suzhou 215123, China 4 Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA Correspondence to: Ping-Kun Zhou, e-mail: zhoupk@bmi.ac.cn Zeng-Fu Shang, e-mail: zengfu.shang@suda.edu.cn Keywords: TNKS1BP1, radiation, DNA-PKcs, DNA repair, poly(ADP-ribosyl)ation Received: December 14, 2014 Accepted: January 10, 2015 Published: February 04, 2015 ABSTRACT TNKS1BP1 was originally identified as an interaction protein of tankyrase 1, which belongs to the poly(ADP-ribose) polymerase (PARP) superfamily. PARP members play important roles for example in DNA repair, telomere stability and mitosis regulation. Although the TNKS1BP1 protein was considered to be a poly(ADP-ribosyl)ation acceptor of tankyrase 1, its function is still unknown. Here we firstly identified that TNKS1BP1 was up-regulated by ionizing radiation (IR) and the depletion of TNKS1BP1 significantly sensitized cancer cells to IR. Neutral comet assay, pulsed-field gel electrophoresis, and γH2AX foci analysis indicated that TNKS1BP1 is required for the efficient repair of DNA double-strand breaks (DSB). The TNKS1BP1 protein was demonstrated to interact with DNA-dependent protein kinase (DNA-PKcs) and poly(ADP-ribose) polymerase 1 (PARP-1), by co-immunoprecipitation analysis. Moreover, TNKS1BP1 was shown to promote the association of PARP-1 and DNA-PKcs. Overexpression of TNKS1BP1 induced the autophosphorylation of DNA-PKcs/Ser2056 in a PARP-1 dependent manner, which contributed to an increased capability of DNA DSB repair. Inhibition of PARP-1 blocked the TNKS1BP1-mediated DNA-PKcs autophosphorylation and attenuated the PARylation of DNA-PKcs. TNKS1BP1 is a newly described component of the DNA DSB repair machinery, which provides much more mechanistic evidence for the rationale of developing effective anticancer measures by targeting PARP-1 and DNA-PKcs.