DNA REPAIR IN SPACE, LESSONS LEARNED FROM CANCER THERAPY AND CRISPR KO SCREENS

Kurzfassung

Space radiation and modern particle radiotherapy share a defining feature: exposure to ionizing radiation with qualities that can produce complex, clustered DNA damage and place distinct demands on DNA damage response (DDR) pathways. Yet, we still lack a systematic framework that links radiation quality to specific DNA repair vulnerabilities—and that integrates these vulnerabilities with clinically used genotoxic treatments in a way that supports precision intervention. We present our results on an integrated screening-and-mechanism workflow to map treatment-dependent synthetic lethal interactions in the DDR across space-relevant irradiation conditions and clinically relevant radiotherapy modalities. We use isogenic human cell systems with defined DNA repair and tumor suppressor backgrounds as a controlled platform to interrogate genetic dependencies. Pooled CRISPR-Cas9 screening with a focused DNA repair/chromatin remodelling library is applied under baseline conditions, after exposure to DNA damaging agents, and following irradiation with distinct beam qualities that span conventional photons and particle radiation. To connect screen hits to mechanism, we perform targeted follow-up in selected knockout models and quantify DNA repair kinetics by immunofluorescence microscopy, focusing on the persistence and resolution of damage foci as a function of radiation quality and dose. Across conditions, this approach recovers known DDR interactions and reveals previously unrecognized vulnerabilities that emerge only in specific treatment contexts. Importantly, radiation-quality–dependent dependencies highlight differential pathway requirements—consistent with distinct lesion complexity and repair dynamics—thereby providing a principled route to stratify repair targets for combination strategies. These results were used to build RepairWeb, a web-based visualization tool that enables exploration of genetic dependency networks and synthetic lethal relationships across treatments and sensitivities to radiation qualities. Overall, these results establish a practical framework to understand DNArepair constraints under space-relevant radiation exposure while directly informing precision radiotherapy—especially the rational design of combinations between radiation modality and DDR-targeting interventions to overcome radioresistance.