Ubiquitination in DNA double-strand break repair: Mechanisms, regulation, and therapeutic implications.

DNA double-strand break (DSB) repair depends on tightly coordinated signaling that controls damage recognition, chromatin remodeling, pathway choice, and repair termination. Among the regulatory layers involved, ubiquitination functions as a central organizing axis of the DNA damage response (DDR), directing the ordered assembly, retention, and turnover of repair factors at damaged chromatin. The RNF8-RNF168 ubiquitin cascade represents a core signaling module that amplifies DSB signals and licenses downstream repair programs. In this review, we summarize recent advances in ubiquitin-dependent regulation of DSB repair, focusing on how ubiquitination governs repair factor dynamics and the balance between classical non-homologous end joining (cNHEJ) and homologous recombination (HR). We further discuss SUMO modification as a tightly coupled regulatory layer that cooperates with ubiquitin signaling to fine-tune signal amplitude and duration through coordinated SUMO-ubiquitin interactions and SUMO-targeted ubiquitination. In addition to ubiquitin-centered regulation, emerging crosstalk with phosphorylation, methylation, acetylation, and PARylation further shapes repair timing, pathway commitment, and signal resolution. Finally, we discuss the translational implications of ubiquitin- and SUMO-centered DDR regulation, highlighting how adaptive repair states and acquired resistance to genotoxic therapies create exploitable therapeutic vulnerabilities.