Ray Chaudhuri, ArnabCallen, ElsaDing, XiaGogola, EwaDuarte, Alexandra ALee, Ji-EunWong, NancyLafarga, VanesaCalvo, Jennifer APanzarino, Nicholas JJohn, SamDay, AmandaCrespo, Anna VidalShen, BinghuiStarnes, Linda Mde Ruiter, Julian RDaniel, Jeremy AKonstantinopoulos, Panagiotis ACortez, DavidCantor, Sharon BFernandez-Capetillo, OscarGe, KaiJonkers, JosRottenberg, SvenSharan, Shyam KNussenzweig, André2025-01-212025-01-212016-07-21Nature . 2016 Jul 21;535(7612):382-7.https://hdl.handle.net/20.500.12105/26086Cells deficient in the Brca1 and Brca2 genes have reduced capacity to repair DNA double-strand breaks by homologous recombination and consequently are hypersensitive to DNA-damaging agents, including cisplatin and poly(ADP-ribose) polymerase (PARP) inhibitors. Here we show that loss of the MLL3/4 complex protein, PTIP, protects Brca1/2-deficient cells from DNA damage and rescues the lethality of Brca2-deficient embryonic stem cells. However, PTIP deficiency does not restore homologous recombination activity at double-strand breaks. Instead, its absence inhibits the recruitment of the MRE11 nuclease to stalled replication forks, which in turn protects nascent DNA strands from extensive degradation. More generally, acquisition of PARP inhibitors and cisplatin resistance is associated with replication fork protection in Brca2-deficient tumour cells that do not develop Brca2 reversion mutations. Disruption of multiple proteins, including PARP1 and CHD4, leads to the same end point of replication fork protection, highlighting the complexities by which tumour cells evade chemotherapeutic interventions and acquire drug resistance.We thank A. Bhandoola for discussions; K. Wolcott for flow cytometry; R. Faryabi for help with statistical analysis; T. de Lange for Rif1f/f mice, J. Tainer for PFM39, R. Brosh for WRNi and J. Petrini for Mre11 antibodies. This work was supported by the Intramural Research Program of the National Institutes of Health (NIH), the National Cancer Institute and the Center for Cancer Research, and by a Department of Defense grant to A.N. (BCRP DOD Idea Expansion Award, grant 11557134), and the Netherlands Organization for Scientific Research, the Dutch Cancer Society and the Swiss National Science Foundation to S.V. A.R.C. was supported by a Prospective Researcher Award from Swiss National Science Foundation (PBZHP3 147302) and Human Frontier Science Program Long-Term Fellowship (LT000393/2013). S.C. was supported by NIH grant R01 CA176166-01A1; B.S. was supported by NIH grant R01CA085344; and J.A.D. was supported by a grant to the Center for Protein Research from the Novo Nordisk Foundation (NNF14CC0001).engVoRhttp://creativecommons.org/licenses/by-nc-nd/4.0/HOMOLOGY-DIRECTED REPAIRCONDITIONAL MOUSE MODELMUTANTS -CELLSDNA-DAMAGE53BP1RECOMBINATIONRESISTANCERESECTIONRIF1PTIPAttribution-NonCommercial-NoDerivatives 4.0 International274437405357612382-387Naturehttps://pmc.ncbi.nlm.nih.gov/articles/PMC4959813/open access