USP47 regulates a 53BP1-based complex function in DNA DSB repair

53BP1 is a key DNA repair protein that regulates double strand break (DSB) repair pathway choice. It assembles a complex, whose loss reverses BRCA1 deficient cells sensitivity to PARP1 inhibitors potentially by antagonizing DSB end resection. 53BP1 is critical for immunoglobulin heavy chain class switch recombination (CSR), that is mediated by the generation and repair of DSBs. Here we identify a deubiquitylase, USP47, as a 53BP1 associated protein that regulates its function in these processes. USP47 loss results in 53BP1 protein instability in a proteasome dependent manner and in reduced 53BP1 ionizing radiation induced foci (IRIF). Like 53BP1, USP47 depletion results in enhanced homologous recombination repair, and defective immunoglobulin CSR. It is also required for resistance to DNA damaging agents. We identify a complex of 53BP1, USP47, Fen1, and Recql1 that regulates a microhomology mediated end joining (MMEJ), a repair pathway that is involved in CSR. Altogether, our findings implicate USP47 in DNA DSB repair at least through regulating a novel 53BP1 associated complex.