Abstract P22: C16orf72/HAPSTR1/TAPR1 Interacts with BRCA1 and Senataxin to Regulate R-loops at Stalled Replication Forks and Confer Resistance to PARP Disruption

Abstract Poly (ADP-ribose) polymerase (PARP) proteins play a crucial role in DNA repair, and their inhibition is toxic in cells with defects in homologous recombination (HR). Whilst this interaction is well-established, other synthetic lethal interactions with PARP1/PARP2 disruption are poorly explored. Hence, we performed a genome-wide CRISPR screen to identify genes which are synthetic lethal with PARP1/PARP2 disruption. We discovered that the uncharacterized C16orf72/HAPSTR1/TAPR1 gene is essential for the survival of PARP1/PARP2 double knock-out cells but not the parental wildtype cells. We further show that C16orf72 is a novel modulator of R-loop and is crucial in facilitating replication fork restart and suppressing DNA damage in response to replication stress. We show that C16orf72 functions in a parallel pathway to PARP1/PARP2 to suppress DNA:RNA hybrids that accumulate at stalled replication forks, and it does this by interacting with BRCA1 and the DNA/RNA helicase Senataxin. Citation Format: Abhishek Bharadwaj Sharma, Muhammad Khairul Ramlee, Joel Kosmin, Martin R. Higgs, Amy Wolstenholme, George E. Ronson, Dylan Jones, Daniel Ebner, Noor Shamkhi, David Sims, Paul W. G. Wijnhoven, Josep Forment, Ian Gibbs-Seymour, Nicholas D. Lakin. C16orf72/HAPSTR1/TAPR1 Interacts with BRCA1 and Senataxin to Regulate R-loops at Stalled Replication Forks and Confer Resistance to PARP Disruption [abstract]. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84(8_Suppl):Abstract nr P22.