Mechanistic insights into RAD51-mediated nucleosome binding and remodeling in homologous recombination

Eukaryotic cells organize their genomic DNA into chromatin to achieve both compact packaging and precise regulation of essential processes, including DNA repair. Depending on the type of damage, distinct repair pathways are activated through the targeted recruitment of repair factors to chromatin. RAD51 is the central recombinase in homologous recombination (HR) and forms nucleoprotein filaments, but its mode of chromatin engagement has remained elusive. In this review, we summarize recent progress in the structural and biochemical understanding of DNA repair within chromatin, with a particular focus on RAD51 and its role in HR. Specifically, we review newly determined cryo-electron microscopy (cryo-EM) structures of RAD51 bound to nucleosomes, revealing how RAD51 assembles on chromatin, recognizes DNA damage sites, and remodels nucleosomes into filamentous intermediates. We summarize current insights into how HR-associated proteins regulate RAD51 activity on chromatin, ensuring the fidelity of each step in HR. We conclude by outlining future directions for elucidating the downstream mechanisms of RAD51-mediated HR in the chromatin context.