TOPOVIBL function in meiotic DSB formation: new insights from its biochemical and structural characterization

Abstract

The TOPOVIL complex catalyzes the formation of DNA double strand breaks (DSB) that initiate meiotic homologous recombination, an essential step for chromosome segregation and genetic diversity during gamete production. TOPOVIL is composed of two subunits (SPO11 and TOPOVIBL) and is evolutionarily related to the archaeal TopoVI topoisomerase complex. SPO11 is the TopoVIA subunit orthologue and carries the DSB formation catalytic activity. TOPOVIBL shares homology with the TopoVIB ATPase subunit. TOPOVIBL is essential for meiotic DSB formation, but its molecular function remains elusive, partly due to the lack of biochemical studies. Here, we purified TOPOVIBLΔC25 and characterized its structure and mode of actionin vitro. Our structural analysis revealed that TOPOVIBLΔC25 adopts a dynamic conformation in solution and our biochemical study showed that the protein remains monomeric upon incubation with ATP, which correlates with the absence of ATP binding. Moreover, TOPOVIBLΔC25 interacted with DNA, with a preference for some geometries, suggesting that TOPOVIBL senses specific DNA architectures. Altogether, our study identified specific TOPOVIBL features that might help to explain how TOPOVIL function evolved toward a DSB formation activity in meiosis.

Structural basis for plasmid restriction by SMC JET nuclease

“…This alignment requires considerable DNA deformations including DNA kinking at the mid-point (Figures 5A, C) likely facilitating DNA access to active site residues. It remains to be elucidated whether such DNA deformations are also needed for accessing the active site of other JET nucleases and the more distantly related Toprim-containing enzymes topoisomerase VI and Spo11 27,38,39 (Figure S11C). AFM images of Spo11-DNA particles and modelling of dimeric complexes from a cryo-EM structure of a monomeric core complex are indeed consistent with the notion of DNA bending 38,40 .…”