Abstract B29: LRP16 is an essential mediator for DNA double-strand breaks induced NF-kappaB activation

DNA double-strand breaks (DSBs) are an intermediate in several important processes, such as V(D)J recombination, class-switch recombination, and meiosis; and a byproduct of a number of both normal or pathological conditions, such as metabolic respiration and inflammation. Thus, the determination of the proper fates of cells with this specific type of DNA damage, i.e., to repair and survive or to die, constitutes an important element in the homeostasis of individual mammals. The activation of NF-kappaB has emerged as an important mechanism for the modulation of the response to DSBs. The concomitant SUMOylation and phosphorylation of IKKgamma; by the SUMO E3 ligase protein inhibitor of activated STAT (PIASy) and the phosphorylation by ataxia telangiectasia mutated (ATM), respectively, is a key event in this mechanism. However, IKKgamma SUMOylation or phosphorylation can occur separately without activating NF-kappaB. Thus, the mechanism through which mammalian cells are able to accomplish these IKKgamma modifications in a timely and lesion-specific manner remains unclear. In this study, we demonstrate that LRP16 constitutively interacts with PARP1 and IKKgamma. This interaction is essential for efficient interactions among PARP1, IKKgamma, and PIASy, the modifications of IKKgamma, and the activation of NF-kappaB following DSB induction. The regulation of LRP16 in NF-kappaB activation is dependent on its poly (ADP-ribose) binding capability through the unique macro domain. The depletion of the DSB-specific sensor Ku80 resulted in a significant reduction in the physical interactions among LRP16, PARP1 and IKKgamma. Additionally, the knockdown of either endogenous Ku80 or Ku70 by siRNA markedly diminished DSB-induced NF-kappaB reporter gene activity and NF-kappaB target gene expression. These data strongly suggest that LRP16, through its constitutive interactions with PARP1 and IKKgamma, functions to facilitate the lesion-specific recruitment of PARP1 and IKKgamma and, ultimately, the concomitant recruitment of PIASy to IKKgamma in response to DSB damage. Therefore, the study has provided important new mechanistic insights concerning DSB-induced NF-kappaB activation. Citation Format: Zhiqiang Wu, Chunmeng Wang, Miaomiao Bai, Xiaolei Li, Qian Mei, Xiang Li, Yao Wang, Xiaobing Fu, Guangbin Luo, Weidong Han. LRP16 is an essential mediator for DNA double-strand breaks induced NF-kappaB activation. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B29.