Abstract
Genome stability depends on the accurate repair of DNA double-strand breaks (DSBs). While chromatin-based mechanisms have been well studied, emerging evidence reveals that nuclear mechanics actively shape repair outcomes, although the mechanisms remain unclear. Here we identify microtubule acetylation as a regulator of nuclear mechanics that promotes DSB repair via homologous recombination (HR). DNA damage induces progressive tubulin acetylation, leading to displacement of the perinuclear vimentin cage. Loss of the vimentin cage softens the nucleus and renders the nuclear envelope responsive to microtubule forces, which drives transient nuclear shape fluctuations, localized DSB mobility and repair. Inhibiting tubulin acetylation abolishes these fluctuations, restricts DSB mobility and negatively impacts the homology search during HR, leaving non-homologous end joining intact. Consequently, persistent DSBs coalesce and cluster at the nuclear periphery, triggering cell-cycle arrest and senescence and increasing sensitivity to DNA-damaging agents. Removal of the vimentin cage is sufficient to rescue these effects, with restored nuclear fluctuations and repair efficiency. Thus, we propose that nuclear fluctuations act as a mechanical strategy to accelerate error-free repair. These findings reveal how cytoskeletal forces shape nuclear function and establish nuclear fluctuations as a fundamental principle for maintaining genome stability.