Reconstitution of the meiotic DNA double strand break complex and activity in vitro – Topobreaks

Molecular mechanism of DNA breaks formation during meiosis

Sexual reproduction requires a specialized type of cell division called meiosis that allows the conversion of diploid cells into haploid gametes. In most species, this requires a specific program of DNA double strand break (DSB) formation and repair by homologous recombination. Meiotic DSBs are catalyzed by the evolutionarily conserved SPO11 protein, an orthologue of the catalytic subunit of the type II DNA topoisomerase TopoVI (TopoVIA). We have recently discovered a key protein that forms a complex with SPO11 and shares strong structural similarities with TopoVIB, the second subunit of TopoVI. We named this factor TopoVIB-Like (TOPOVIBL). This discovery provides very strong evidence for a tight molecular relationship between topoisomerase activity and meiotic DSB formation.
The aim of our project is to demonstrate the predicted catalytic activity of the SPO11-TOPOVIBL complex in vitro, to determine whether additional partners are involved, to characterize its molecular architecture and to establish its phylogenetic conservation within the eukaryotic tree. This project has the ambition to elucidate the differences between the complex that initiates meiotic DSBs and the TopoVI enzyme and thus to understand how a classical topoisomerase activity has evolved towards a meiotic DSB activity, a possibly fundamental step for sexual reproduction.