Dimerization of MORC2 through its C-terminal coiled-coil domain enhances chromatin dynamics and promotes DNA repair

Hong-Yan Xie,Da-Qiang Li,Tai-Mei Zhang,Shu-Yuan Hu,Zhi-Ming Shao

doi:10.1186/s12964-019-0477-5

Abstract

Decondesation of the highly compacted chromatin architecture is essential for efficient DNA repair, but how this is achieved remains largely unknown. Here, we report that microrchidia family CW-type zinc finger protein 2 (MORC2), a newly identified ATPase-dependent chromatin remodeling enzyme, is required for nucleosome destabilization after DNA damage through loosening the histone-DNA interaction. Depletion of MORC2 attenuates phosphorylated histone H2AX (γH2AX) focal formation, compromises the recruitment of DNA repair proteins, BRCA1, 53BP1, and Rad51, to sites of DNA damage, and consequently reduces cell survival following treatment with DNA-damaging chemotherapeutic drug camptothecin (CPT). Furthermore, we demonstrate that MORC2 can form a homodimer through its C-terminal coiled-coil (CC) domain, a process that is enhanced in response to CPT-induced DNA damage. Deletion of the C-terminal CC domain in MORC2 disrupts its homodimer formation and impairs its ability to destabilize histone-DNA interaction after DNA damage. Consistently, expression of dimerization-defective MORC2 mutant results in impaired the recruitment of DNA repair proteins to damaged chromatin and decreased cell survival after CPT treatment. Together, these findings uncover a new mechanism for MORC2 in modulating chromatin dynamics and DDR signaling through its c-terminal dimerization.

Highlights

DNA is continuously challenged by both endogenous and exogenous genotoxic agents that induce a variety of DNA lesions
We report that microrchidia family CW-type zinc finger protein 2 (MORC2) loosens histoneDNA interaction and promotes the accessibility of DNA repair machinery to DNA damage lesions, facilitating cell survival after DNA damage induced by DNAdamaging chemotherapeutic agent camptothecin (CPT)
We knocked out MORC2 using the CRISPR/Cas9 system in HeLa and MCF-7 cells, which are widely used in DNA damage-related studies [26] (Fig. 1a), and analyzed the effects of MORC2 depletion on the interactions between histone and DNA using salt solubilization assays [27, 28]

Summary

Introduction

DNA is continuously challenged by both endogenous and exogenous genotoxic agents that induce a variety of DNA lesions. Inefficient or inaccurate repair of these genotoxic lesions is intimately implicated in genomic instability and carcinogenesis [1]. Cells have developed a complex molecular network, termed the DNA damage response (DDR), to detect and repair damaged DNA in the context of chromatin [2]. Chromatin is a highly condensed structure that presents a significant barrier to the ability of the DNA repair machinery to access and repair DNA lesions [3,4,5]. Damaged chromatin must become more accessible to enable DNA repair [5, 6].

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Results

Conclusion