Wilson lab paper featured in Nature communications. Authors Image In a collaborative paper between the Wilson lab and Jackson lab (Gurdon Institute) the authors explain how homologous recombination can be restored in cells lacking key DNA damage regulators 53BP1 and BRCA1, which is a common mutation spectrum found in drug resistant breast cancers. They found that the DNA damage repair factor PALB2 is still able to promote homologous recombination and this required direct interaction with chromatin via interaction between PALB2 and the nucleosome acidic patch. Belotserkovskaya, R., Raga Gil, E., Lawrence, N., Butler, R., Clifford, G., Wilson, M. D., & Jackson, S. P. Summary of Paper by Lori Koch The BRCA1 protein promotes repair of DNA double-strand breaks by homologous recombination. Following treatment of BRCA1-deficient cancers with PARP inhbitors, resistant cells can appear, commonly with mutations in the DNA double-strand break repair protein 53BP1. However, how loss of 53BP1 rescues BRCA1- cells was unclear. In a study published in Nature Communications, WCB scientists Marcus Wilson and Gillian Clifford worked with colleagues at the Gurdon Institute, University of Cambridge, to investigate the mechanisms used by BRCA1-deficient cells to repair DNA double-strand breaks. Using fluorescence imaging, they found that loss of 53BP1 restores the formation of RAD51 filaments, required for repair, at break sites in BRCA1-deficient cells. Next, they found that the repair protein PALB2 was more strongly recruited to sites of double-strand breaks in BRCA1- and 53BP1- doubly deficient cells. Given that PALB2 is known to bind chromatin, the authors investigated whether association of PALB2 with chromatin was required for its function in DNA repair in the BRCA1- and 53BP1- deficient cells. They created mutations in two regions of PALB2 previously identified as important for its interaction with chromatin. Experiments with various mutants showed that the ChAM domain in PALB2 was particularly important for double-strand break repair in cells lacking both BRCA1 and 53BP1. To investigate the binding of PALB2 to chromatin further, Centre scientists Marcus Wilson and Gillian Clifford purified nucleosome core particles and PALB2 proteins and carried out in vitro binding assays. These experiments showed that the ChAM domain was sufficient to bind to nucleosomes in vitro. Additionally, they localised the interaction to an acidic patch on the nucleosome, and a corresponding basic patch in the ChAM domain. In sum, the study illuminates several new aspects of how BRCA1- deficient cells respond to DNA damage. Related links Journal Link Wilson Lab Website DOI This article was published on 2024-06-17
