DNA damage: ubiquitin marks the spot

DNA damage activates signaling cascades driven by the ATM-ATR protein kinases, culminating in the recruitment of repair proteins to the damage site through poorly understood mechanisms. Now a flurry of papers reveals how ATM-dependent phosphorylation of mediator and chromatin-associated proteins at sites of double-strand breaks promotes ubiquitylation of local nucleosomes, thereby eliciting a powerful signal for recruitment of repair complexes to the damage site.