Abstract
Meiosis-specific Rec114−Mei4 and Mer2 complexes are thought to enable Spo11-mediated DNA double-strand break (DSB) formation through a mechanism that involves DNA-dependent condensation. However, the structure, molecular properties, and evolutionary conservation of Rec114−Mei4 and Mer2 are unclear. Here, we present AlphaFold models of Rec114−Mei4 and Mer2 complexes supported by nuclear magnetic resonance (NMR) spectroscopy, small-angle X-ray scattering (SAXS), and mutagenesis. We show that dimers composed of the Rec114 C terminus form α-helical chains that cup an N-terminal Mei4 α helix, and that Mer2 forms a parallel homotetrameric coiled coil. Both Rec114−Mei4 and Mer2 bind preferentially to branched DNA substrates, indicative of multivalent protein–DNA interactions. Indeed, the Rec114−Mei4 interaction domain contains two DNA-binding sites that point in opposite directions and drive condensation. The Mer2 coiled-coil domain bridges coaligned DNA duplexes, likely through extensive electrostatic interactions along the length of the coiled coil. Finally, we show that the structures of Rec114−Mei4 and Mer2 are conserved across eukaryotes, while DNA-binding properties vary significantly. This work provides insights into the mechanism whereby Rec114−Mei4 and Mer2 complexes promote the assembly of the meiotic DSB machinery and suggests a model in which Mer2 condensation is the essential driver of assembly, with the DNA-binding activity of Rec114−Mei4 playing a supportive role.
Funder
European Research Council
Fonds National de la Recherche Scientifique
FNRS
FRIA
FWO-Vlaanderen
Publisher
Cold Spring Harbor Laboratory
Subject
Developmental Biology,Genetics
Cited by
9 articles.
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