Abstract
53BP1 is recruited to chromatin in the vicinity of DNA double-strand breaks (DSBs). We identify the nuclear kinesin, KIF18B, as a 53BP1-interacting protein and define its role in 53BP1-mediated DSB repair. KIF18B is a molecular motor protein involved in destabilizing astral microtubules during mitosis. It is primarily nuclear throughout the interphase and is constitutively chromatin bound. Our observations indicate a nuclear function during the interphase for a kinesin previously implicated in mitosis. We identify a central motif in KIF18B, which we term the Tudor-interacting motif (TIM), because of its interaction with the Tudor domain of 53BP1. TIM enhances the interaction between the 53BP1 Tudor domain and dimethylated lysine 20 of histone H4. TIM and the motor function of KIF18B are both required for efficient 53BP1 focal recruitment in response to damage and for fusion of dysfunctional telomeres. Our data suggest a role for KIF18B in efficient 53BP1-mediated end-joining of DSBs.
Highlights
DNA double-strand breaks (DSBs) activate the DNA-damage response (DDR), involving a cascade of protein recruitments and post-translational modifications (PTMs), which result in DSB repair via two distinct pathways, non-homologous end joining (NHEJ) and homologous recombination (HR) (Blackford and Jackson, 2017; Schwertman et al, 2016)
We show that KIF18B binds to the Tudor domain of 53BP1 and stimulates its H4K20me2-binding function via a Tudor-interacting motif (TIM)
KIF18B is required for 53BP1-mediated DSB repair Based on a previous strategy (Pessina and Lowndes, 2014), we used stable isotope labeling by amino acids in cell culture (SILAC) quantitative proteomics in chicken DT40 cells to identify partners of 53BP1 (Table S1; STAR Methods)
Summary
DNA double-strand breaks (DSBs) activate the DNA-damage response (DDR), involving a cascade of protein recruitments and post-translational modifications (PTMs), which result in DSB repair via two distinct pathways, non-homologous end joining (NHEJ) and homologous recombination (HR) (Blackford and Jackson, 2017; Schwertman et al, 2016). The recruitment of 53BP1 to DSBs is dependent on two distinct histone PTMs: the constitutive H4K20me, and the DNA damage-inducible H2AK15ub (Sanders et al, 2004; Wilson and Durocher, 2017). The interaction of 53BP1 with modified histones flanking DSBs is subject to complex regulation that is incompletely understood. H2AK15ub is induced in response to DSBs via RNF168 (Mattiroli et al, 2012), H4K20me is largely a constitutive histone modification (Pei et al, 2011; Sanders et al, 2004). The reversible complex between 53BP1 and Tudor-interacting repair regulator (TIRR) blocks the H4K20me2-binding surface of 53BP1 (Draneet al., 2017)
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