Genetic Regulation of DNA Double-Strand Breaks and Repair Pathways

DNA double-strand breaks (DSB) represent one of the most severe forms of genomic damage. Thus, cells have evolved a complex network of DSB repair pathways, including homologous recombination, classical and alternative end joining, and single-strand annealing, which are tightly regulated by genetic and epigenetic factors. The selection and efficiency of these pathways influence genome integrity, oncogenesis, and therapeutic response. This comprehensive review synthesizes recent findings on the genetic regulation of DSB repair, with emphasis on pathway-specific regulators, chromatin context, and post-translational modifications. Moreover, this review integrates primary research from mammalian systems, including CRISPR-based studies, proteomics, and imaging, with a focus on publications from 2020 to 2025. We discuss the role of key players, such as MRE11-RAD50-NBS1 (MRN), ataxia telangiectasia mutated (ATM), mediator tumor suppressor p53-binding protein 1 (53BP1), breast cancer type 1 susceptibility protein (BRCA1), anti-silencing function 1 (ASF1), ring finger protein (RNF)8/168, DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and RAD51 recombinase (RAD51), in orchestrating the associated pathway choice. Epigenetic modifications, RNA-mediated mechanisms, and chromatin remodeling dynamically influence the efficiency and fidelity of repair. Particular attention is provided to emerging regulators, including thyroid hormone receptor interactor 13 (TRIP13), ubiquitin-like with plant homeodomain (PHD) and RING finger domains 1 (UHRF1), Shieldin, and polymerase theta. This review highlights novel insights into transcription-associated DSB repair, the interplay of replication stress with repair pathway engagement, and context-dependent synthetic lethality. We also examine implications for cancer biology, including therapy resistance and biomarker development. Ultimately, understanding the genetic regulation of DSB repair pathways can provide critical insights into genome stability maintenance and reveal new therapeutic opportunities in cancer. Future work should focus on pathway crosstalk, phase-specific regulation, and integrating repair modulation into personalized medicine.