"The eukaryotic Topoisomerase3 (TopIII) belongs to the replicative machinery present at the replication fork. TopIII is a type 1 enzyme whose activity is known to unlink the DNA single strand catenanes as shown by the crystal structure of the E. coli Topoisomerase III solved in 2001. The TopIII propensity to solve DNA topological problems and to complete homologous recombination events during replication made of it a key component in genome stability and integrity. The atomic mechanisms of TopIII activity as well as its regulation are still poorly understood. To this point of view, increasing number of studies have highlighted a new TopIII binding partner, the RMI1 (RecQ mediated genome instability) protein, which could recruit and/or regulate TopIII activity by physical interaction. RMI1 is an OB (Oligonucleotide Binding) fold protein part of the RMI complex. This complex is composed, in eukaryotic organisms, of RMI1 and RMI2 except in the Saccharomyces cerevisiae yeast which only possesses RMI1. We propose to unravel the molecular interaction between Saccharomyces cerevisiae TopIII and RMI1 by a combination of biochemical and crystallographic approaches. The main aim of my post-doctorat project is to express in the Baculovirus/Insect cells heterologous system the TopIII/RMI1 complex, to purify and crystallize it in presence of DNA. To obtain a crystal structure of such a complex could allow to better understand the influence of the RMI protein on the TopIII conformation and activity and maybe its role in shunting the complex toward a specific pathway during homologous recombination or other DNA metabolism reaction."