Mre11 Is Essential for the Removal of Lethal Topoisomerase 2 Covalent Cleavage Complexes

• Published in: Molecular cell Vol. 64; no. 3; pp. 580 - 592
• Main Authors: Hoa, Nguyen Ngoc, Shimizu, Tsubasa, Zhou, Zhong Wei, Wang, Zhao-Qi, Deshpande, Rajashree A., Paull, Tanya T., Akter, Salma, Tsuda, Masataka, Furuta, Ryohei, Tsutsui, Ken, Takeda, Shunichi, Sasanuma, Hiroyuki
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 03.11.2016
• Subjects: Acid Anhydride Hydrolases; Animals; Antigens, Neoplasm - genetics; Antigens, Neoplasm - metabolism; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Death - drug effects; Cell Line, Tumor; Chickens; DNA - genetics; DNA - metabolism; DNA Breaks, Double-Stranded - drug effects; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; DNA Topoisomerases, Type II - genetics; DNA Topoisomerases, Type II - metabolism; DNA-Binding Proteins - deficiency; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; etoposide; Etoposide - pharmacology; Gene Expression Regulation; Genomic Instability - drug effects; Humans; Lymphocytes - cytology; Lymphocytes - drug effects; Lymphocytes - metabolism; Mre11 and nonhomologous end joining; MRE11 Homologue Protein; Mutation; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phosphoric Diester Hydrolases; Poly-ADP-Ribose Binding Proteins; Recombinational DNA Repair - drug effects; Signal Transduction; Topoisomerase II Inhibitors - pharmacology; Transcription Factors - genetics; Transcription Factors - metabolism; Mre11 and nonhomologous end joining; etoposide
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2016.10.011

The Mre11/Rad50/Nbs1 complex initiates double-strand break repair by homologous recombination (HR). Loss of Mre11 or its nuclease activity in mouse cells is known to cause genome aberrations and cellular senescence, although the molecular basis for this phenotype is not clear. To identify the origin of these defects, we characterized Mre11-deficient (MRE11−/−) and nuclease-deficient Mre11 (MRE11−/H129N) chicken DT40 and human lymphoblast cell lines. These cells exhibit increased spontaneous chromosomal DSBs and extreme sensitivity to topoisomerase 2 poisons. The defects in Mre11 compromise the repair of etoposide-induced Top2-DNA covalent complexes, and MRE11−/− and MRE11−/H129N cells accumulate high levels of Top2 covalent conjugates even in the absence of exogenous damage. We demonstrate that both the genome instability and mortality of MRE11−/− and MRE11−/H129N cells are significantly reversed by overexpression of Tdp2, an enzyme that eliminates covalent Top2 conjugates; thus, the essential role of Mre11 nuclease activity is likely to remove these lesions. [Display omitted] •Topoisomerase 2 (Top2) frequently fails to complete catalysis•Failed catalysis causes the formation of Top2-cleavage complex (Top2cc)•Mre11 nuclease eliminates Top2cc followed by DNA double-strand break repair•Top2cc accumulation leads mitotic chromosomal breakage and apoptosis The MRN complex is critical for genomic stability through several mechanisms. Hoa et al. find that nuclease activity of Mre11 is critical for the removal of topoisomerase 2-cleavage complexes that naturally accumulate in the genome when topoisomerase 2 fails to complete catalysis.