The DNA damage response (DDR) is a multi-faceted network of pathways that preserves genome stability. Because endogenous damage is an existential and continual threat, cells achieve robustness by engaging multiple overlapping pathways to deal with it. Addressing this complexity is a daunting challenge because gene functions in essential DNA repair processes can be masked and overlooked when pathways use completely different mechanisms to complement one another.

To tackle this problem, we undertook the most systematic genetic interaction investigation of the human DDR to date. We used dual guide CRISPR interference (CRISPRi) screening to query pairwise interactions of all core GO-annotated DDR genes spanning all DDR pathways, interrogating 679,233 unique guide RNA pairs and 149,878 gene combinations. Thus, we generated a comprehensive genetic interaction map of the human DDR, which we made available at https://spidrweb.org/.  Our data yield fundamental insights into genome maintenance, provide a springboard for mechanistic investigations into new connections between DDR factors, and pinpoint synthetic vulnerabilities that could be exploited in cancer therapy

I will summarize our CRISPRi screening work and highlight its many applications. I will also present data defining the molecular mechanism for one of the strongest, novel synthetic lethal interactions we identified between the DNA translocases, SMARCAL1 and FANCM.