%0 Journal Article %A Deiss, Katharina %A Lockwood, Nicola %A Howell, Michael %A Segeren, Hendrika Alida %A Saunders, Rebecca E %A Chakravarty, Probir %A Soliman, Tanya N %A Martini, Silvia %A Rocha, Nuno %A Semple, Robert %A Zalmas, Lykourgos-Panagiotis %A Parker, Peter J %D 2019 %T A genome-wide RNAi screen identifies the SMC5/6 complex as a non-redundant regulator of a Topo2a-dependent G2 arrest %U https://crick.figshare.com/articles/journal_contribution/A_genome-wide_RNAi_screen_identifies_the_SMC5_6_complex_as_a_non-redundant_regulator_of_a_Topo2a-dependent_G2_arrest/11357801 %2 https://crick.figshare.com/ndownloader/files/20160752 %K Cell Cycle Proteins %K Cell Line %K Chromosomal Proteins, Non-Histone %K DNA Damage %K DNA Topoisomerases, Type II %K Fibroblasts %K G2 Phase Cell Cycle Checkpoints %K Genome, Human %K Germ-Line Mutation %K Humans %K Ligases %K Multiprotein Complexes %K Piperazines %K Poly-ADP-Ribose Binding Proteins %K RNA Interference %K Sumoylation %K Ubiquitin-Protein Ligases %K Parker FC001130 %K Swanton FC001169 %K HTS %K CB %K PC-ack %K FC-ack %K CS-ack %K LM-ack %K Developmental Biology %K 05 Environmental Sciences %K 06 Biological Sciences %K 08 Information and Computing Sciences %X The Topo2a-dependent arrest is associated with faithful segregation of sister chromatids and has been identified as dysfunctional in numerous tumour cell lines. This genome-protecting pathway is poorly understood and its characterization is of significant interest, potentially offering interventional opportunities in relation to synthetic lethal behaviours in arrest-defective tumours. Using the catalytic Topo2a inhibitor ICRF193, we have performed a genome-wide siRNA screen in arrest-competent, non-transformed cells, to identify genes essential for this arrest mechanism. In addition, we have counter-screened several DNA-damaging agents and demonstrate that the Topo2a-dependent arrest is genetically distinct from DNA damage checkpoints. We identify the components of the SMC5/6 complex, including the activity of the E3 SUMO ligase NSE2, as non-redundant players that control the timing of the Topo2a-dependent arrest in G2. We have independently verified the NSE2 requirement in fibroblasts from patients with germline mutations that cause severely reduced levels of NSE2. Through imaging Topo2a-dependent G2 arrested cells, an increased interaction between Topo2a and NSE2 is observed at PML bodies, which are known SUMOylation hotspots. We demonstrate that Topo2a is SUMOylated in an ICRF193-dependent manner by NSE2 at a novel non-canonical site (K1520) and that K1520 sumoylation is required for chromosome segregation but not the G2 arrest. %I The Francis Crick Institute