Lighting ATR/Chk1 by mesoscale TopBP1 condensates.

Biomolecular condensation has gained considerable attention as a fundamental mechanism in cell signaling and various biological processes. A recent study by Egger et al. provides valuable insights into the constituents of topoisomerase IIβ binding protein 1 (TopBP1) condensates and sheds light on the mechanism of Chk1 activation by ataxia telangiectasia-mutated and Rad3-related (ATR) at the interface of these condensates.