ERCC1-XPF Interacts with Topoisomerase IIβ to Facilitate the Repair of Activity-induced DNA Breaks

Type II DNA Topoisomerases (TOP II) generate transient double-strand DNA breaks (DSBs) to resolve topological constraints during transcription. Using genome-wide mapping of DSBs and functional genomics approaches, we show that, in the absence of exogenous genotoxic stress, transcription leads to DSB accumulation and to the recruitment of the structure-specific ERCC1-XPF endonuclease on active gene promoters. Instead, we find that the complex is released from regulatory or gene body elements in UV-irradiated cells. Abrogation of ERCC1 or re-ligation blockage of TOP II-mediated DSBs aggravates the accumulation of transcription-associated {gamma}H2Ax and 53BP1 foci, which dissolve when TOP II-mediated DNA cleavage is inhibited. An in vivo biotinylation tagging strategy coupled to a high-throughput proteomics approach reveals that ERCC1-XPF interacts with TOP II{beta} and the CTCF/cohesin complex, which co-localize with the heterodimer on DSBs. Together; our findings provide a rational explanation for the remarkable clinical heterogeneity seen in human disorders with ERCC1-XPF defects.