Janssen, L. M. E.; Baltasar Perez, E.; Vaarting, C.; Mazouzi, A.; Raaben, M.; Brummelkamp, T. R.; Medema, R. H.; Raaijmakers, J.

High fidelity of replication is important to preserve genomic integrity and ensure healthy progeny. Perturbations of replication, also known as replication stress, is frequently observed in cancer cells and is considered a cancer cell-specific trait. Although replication stress drives genomic instability and tumor progression, it also generates a targetable cancer-specific vulnerability. In order to identify potential therapeutic targets in cancer cells that experience replication stress, we performed a genome wide genetic screen in human HAP1 cells challenged with low doses of replication stress-inducing drugs. We identified a large set of genes that specifically hamper cell survival in the context of replication stress. In addition to well-known players in the replication stress response and DNA repair, such as RNASEH1, BRIP1, and MDC1, we identified several genes with no prior described role in DNA replication, damage tolerance or repair. We validated that the loss of GIGYF2, HNRNPA2B1, and SUMO2 renders cells more vulnerable to replication stress. For GIGYF2 and SUMO2, we could implicate a role in homologous recombination. Taken together, our replication stress screen identified several known as well as some novel factors that protect against the toxic implications of replication stress. These factors could entail potential therapeutic targets for cancer cells experiencing replication stress.