DNA-driven condensation assembles the meiotic DNA break machinery

Accurate segregation of chromosomes during meiosis—critical for genome stability across sexual cycles—relies on homologous recombination initiated by DNA double-strand breaks (DSBs) made by the Spo11 protein(1,2). DSB formation is regulated and tied to the elaboration of large-scale chromosome structures(3–5), but the protein assemblies that execute and control DNA breakage are poorly understood. We address this through molecular characterization of Saccharomyces cerevisiae RMM proteins (Rec114, Mei4 and Mer2)—essential, conserved components of the DSB machinery(2). Each subcomplex of Rec114–Mei4 (a 2:1 heterotrimer) or Mer2 (a coiled-coil-containing homotetramer) is monodisperse in solution, but they independently condense with DNA into reversible nucleoprotein clusters that share properties with phase-separated systems. Multivalent interactions drive condensation. Mutations that weaken protein–DNA interactions strongly disrupt both condensate formation and DSBs in vivo, strongly correlating these processes. In vitro, condensates fuse into mixed RMM clusters that further recruit Spo11 complexes. Our data show how the DSB machinery self-assembles on chromosome axes to create centers of DSB activity. We propose that multilayered control of Spo11 arises from the recruitment of regulatory components and modulation of biophysical properties of the condensates.