DNA double-strand breaks come into focus.

The Mre11-Rad50-Nbs1 (MRN) complex senses DNA double-strand breaks and recruits different repair pathway and checkpoint proteins to break foci. Two new studies (Williams et al., 2009; Lloyd et al., 2009) identify Nbs1 as a key factor in this process and reveal how an N-terminal protein recruitment module in Nbs1 binds to different response factors through shared phosphopeptide motifs.