Probing DNA damage sites reveals context-dependent and novel DNA damage response factors

DNA damage is a constant threat to genome integrity and function. Diminished capacity for DNA repair is linked to many human diseases, therefore understanding the molecular pathways responding to DNA damage is key for developing novel therapies. Lack of unbiased probes to report DNA damage dynamics and the associated proteins in living cells and animals limit our current efforts to completely understand DNA repair processes. In this study we overcome these limitations by engineering protein probes containing the tandem-BRCT domain of MCPH1, which we show to have a specific affinity for the DNA-damage-associated histone mark γH2AX. We employ these probes to track DNA damage dynamics in living cells exposed to a panel of different genotoxic insults and to visualize programmed double strand breaks during gametogenesis in living animals. We further utilize the binding selectivity of our probe to tether TurboID biotin ligases to chromatin and identify the DNA damage-associated proteome via proximity ligation. By comparing five different DNA damaging agents, we reveal the proteome associated with specific lesions, and identify multiple novel proteins with potential implications in damage response and repair. Among these novel proteins, we characterize the ubiquitin ligase UBE3A, the methyl-binding and proteasome-recruiting protein L3MBTL3, and the spliceosomal factor U2SURP, as previously uncharacterized effectors of DNA damage response. These functional datasets reveal the DNA damage-dependent proteomes and reveal novel insights into DNA damage response.