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Zong D , Adam S , Wang Y , Sasanuma H , Callen E , Murga M , Day A , Kruhlak MJ , Wong N , Munro M , Ray Chaudhuri A , Karim B , Xia B , Takeda S , Johnson N , Durocher D , Nussenzweig A
BRCA1 Haploinsufficiency Is Masked by RNF168-Mediated Chromatin Ubiquitylation
Mol Cell. 2019 Mar 21;73(6) :1267-1281 e7
PMID: 30704900    PMCID: PMC6430682    URL: https://www.ncbi.nlm.nih.gov/pubmed/30704900
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BRCA1 functions at two distinct steps during homologous recombination (HR). Initially, it promotes DNA end resection, and subsequently it recruits the PALB2 and BRCA2 mediator complex, which stabilizes RAD51-DNA nucleoprotein filaments. Loss of 53BP1 rescues the HR defect in BRCA1-deficient cells by increasing resection, suggesting that BRCA1's downstream role in RAD51 loading is dispensable when 53BP1 is absent. Here we show that the E3 ubiquitin ligase RNF168, in addition to its canonical role in inhibiting end resection, acts in a redundant manner with BRCA1 to load PALB2 onto damaged DNA. Loss of RNF168 negates the synthetic rescue of BRCA1 deficiency by 53BP1 deletion, and it predisposes BRCA1 heterozygous mice to cancer. BRCA1(+/-)RNF168(-/-) cells lack RAD51 foci and are hypersensitive to PARP inhibitor, whereas forced targeting of PALB2 to DNA breaks in mutant cells circumvents BRCA1 haploinsufficiency. Inhibiting the chromatin ubiquitin pathway may, therefore, be a synthetic lethality strategy for BRCA1-deficient cancers.
1097-4164 Zong, Dali Adam, Salome Wang, Yifan Sasanuma, Hiroyuki Callen, Elsa Murga, Matilde Day, Amanda Kruhlak, Michael J Wong, Nancy Munro, Meagan Ray Chaudhuri, Arnab Karim, Baktiar Xia, Bing Takeda, Shunichi Johnson, Neil Durocher, Daniel Nussenzweig, Andre Journal Article United States Mol Cell. 2019 Mar 21;73(6):1267-1281.e7. doi: 10.1016/j.molcel.2018.12.010. Epub 2019 Jan 28.