Genome-wide and high-density CRISPR-Cas9 screens identify point mutations in PARP1 causing PARP inhibitor resistance

Prof. Christopher Lord, Stephen Pettitt, Dr. Dragomir Krastev, Inger Brandsma, Amy Drean, Feifei Song, Radoslav Aleksandrov, Maria Harrell, Malini Menon, Rachel Brough, Dr. James Campbell, Dr. Jessica Frankum, Dr. Michael Ranes, Ms. Helen Pemberton, Rumana Rafiq, Dr. Kerry Fenwick, Amanda Swain, Dr. Sebastian Guettler, Jung-Min Lee, Elizabeth Swisher, Stoyno Stoynov, Dr. Kosuke Yusa, Dr. Alan Ashworth

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Received: 29th September 17

PARP inhibitors (PARPi) target homologous recombination defective tumour cells via synthetic lethality. Genome-wide and high-density CRISPR-Cas9 “tag, mutate and enrich” mutagenesis screens identified single amino acid mutations in PARP1 that cause profound PARPi-resistance. These included PARP1 mutations outside of the DNA interacting regions of the protein, such as mutations in solvent exposed regions of the catalytic domain and clusters of mutations around points of contact between ZnF, WGR and HD domains. These mutations altered PARP1 trapping, as did a mutation found in a clinical case of PARPi resistance. These genetic studies reinforce the importance of trapped PARP1 as a key cytotoxic DNA lesion and suggest that interactions between non-DNA binding domains of PARP1 influence cytotoxicity. Finally, different mechanisms of PARPi resistance (BRCA1 reversion, PARP1, 53BP1, REV7 mutation) had differing effects on chemotherapy sensitivity, suggesting that the underlying mechanism of PARPi resistance likely influences the success of subsequent therapies.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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