Mitosis-specific role of ATR The ATR (ataxia telangiectasia mutated and Rad3-related) kinase plays important roles in the S phase and during the DNA damage response to safeguard genome integrity. Kabeche et al. identified a distinct ATR activation pathway in mitosis that is also critical for suppressing genome instability (see the Perspective by Saldivar and Cimprich). ATR is recruited by Aurora A and activated by R loops at centromeres of mitotic chromosomes; this leads to Aurora B activation, which is necessary for accurate chromosome segregation. This mitotic, R loop–driven ATR signaling pathway could potentially be exploited in the search for cancer therapeutics. Science , this issue p. 108 ; see also p. 30