DNA-driven condensation assembles the meiotic DNA break machinery

Abstract

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.

Conservation and divergence of meiotic DNA double strand break forming mechanisms in Arabidopsis thaliana

“…Our finding that MLH1 and late HEI10 foci numbers are increased in the absence of PHS1 supports this idea (Figure 5 and Supplementary Figure S7 ). A finding also in agreement with the recent discovery that, In S. cerevisiae , the RMM proteins form clusters on which the other DSB proteins as well as additional regulatory proteins could be recruited, promoting not only the assembly and the activation of the DSB core complex but, possibly, also regulating further steps of DSB repair ( 99 ).…”

Control of Chromatin Organization and Chromosome Behavior during the Cell Cycle through Phase Separation

“…In Caenorhabditis elegans, multivalent weak interactions between synap tonemal complex (SC) units drive SC formation, and the SC exhibits phase separatio properties [8]. DNA-driven condensation assembles the meiotic DNA double-stran break machinery, the multilayer control of Spo11 resulting from the recruitment of regu latory components, and the modulation of the biophysical properties of the condensat [9]. In mammalian oocytes, a liquid-like spindle structural domain facilitates spindle as sembly [10].…”

A Hypothesis: Linking Phase Separation to Meiotic Sex Chromosome Inactivation and Sex-Body Formation

“…Liquid-liquid phase separation is a driver for the assembly of membraneless biomolecular condensates in cells. It exerts a variety of functions, including sequestration of molecules, buffering molecule concentration, regulating the specificity and kinetics of biochemical reactions, genomic organization, RNA processing, and generating meiotic DNA breaks (Banani et al, 2017;Claeys Bouuaert et al, 2021). During male meiosis, sex chromosomes are reorganized, transcriptionally silenced by MSCI, and form a visibly distinct membraneless structure at pachytene stage.…”