Interactome analysis identifies a new paralogue of XRCC4 in non-homologous end joining DNA repair pathway.

Mengtan Xing,Qingsong Wang,Leizhen Wei,Rong Guo,Mei Hou,Ge Gao,Huanhuan Liang,Wenxia Jiang,Dongyi Xu,Zhenxin Yan,Chunxia Dong,Shan Zha,Feng Feng,Wei Huo,Jianguo Ji,Wen Li,Li Lan,Shaokai Ning,Mingrui Yang

doi:10.1038/ncomms7233

Abstract

Non-homologous end joining (NHEJ) is a major pathway to repair DNA double-strand breaks (DSBs), which can display different types of broken ends. However, it is unclear how NHEJ factors organize to repair diverse types of DNA breaks. Here, through systematic analysis of the human NHEJ factor interactome, we identify PAXX as a direct interactor of Ku. The crystal structure of PAXX is similar to those of XRCC4 and XLF. Importantly, PAXX-deficient cells are sensitive to DSB-causing agents. Moreover, epistasis analysis demonstrates that PAXX functions together with XLF in response to ionizing radiation-induced complex DSBs, whereas they function redundantly in response to Topo2 inhibitor-induced simple DSBs. Consistently, PAXX and XLF coordinately promote the ligation of complex but not simple DNA ends in vitro. Altogether, our data identify PAXX as a new NHEJ factor and provide insight regarding the organization of NHEJ factors responding to diverse types of DSB ends.

Highlights

Non-homologous end joining (NHEJ) is a major pathway to repair DNA double-strand breaks (DSBs), which can display different types of broken ends
Our data reveal that paralogue of XRCC4 and XLF (PAXX) is a new core NHEJ factor that plays a key role in the organization of NHEJ complexes for the repair of diverse types of DSB ends
Silver staining (Fig. 1a, lane 4), mass spectrometry (Table 1) and immunoblotting (Fig. 1c) of the reciprocal immunoprecipitation (IP) revealed the presence of major NHEJ proteins, including XLF, XRCC4, Lig[4], Ku70, Ku80 and DNA-PKcs in the PAXX-associated complexes, demonstrating that PAXX is a new component of the NHEJ complex

Summary

Introduction

Non-homologous end joining (NHEJ) is a major pathway to repair DNA double-strand breaks (DSBs), which can display different types of broken ends. It is unclear how NHEJ factors organize to repair diverse types of DNA breaks. For complex or ‘dirty’ breaks, which have mismatched or covalently modified DNA ends, additional factors are required to modify the ends and facilitate their ligation These factors include Artemis, DNA polymerases l and m, terminal dinucletidyltrasferase, polynucleotide kinase-phosphatase, aprataxin (APTX) and APTX–polynucleotide kinase-phosphatase-like factor[1]. Our data reveal that PAXX is a new core NHEJ factor that plays a key role in the organization of NHEJ complexes for the repair of diverse types of DSB ends

Methods

Results

Conclusion