In the course of our work on the control of flagellar formation we showed that flagelin gene expression was controlled by DNA inversion mediated by Hin Recombinase. Our detailed studies of the mechanisms of this reaction have revealed that it involves the formation of nucleo-protein complexes that include multiple proteins associated with specific DNA binding sites. The assembly of similar structures involving elaborated DNA-protein interactions has been implicated in the mechanisms involved in specific gene expression, viral integration and transposition. Hin-Recombinase offers a relatively simple model in which to study the role of "enhancers" and other "factors" in the formation of the complex DNA-protein structures required to achieve efficient, site specific, directional recombination. Our immediate goal is to understand in detail the nature of the Hin Recombinase reaction, i.e. the mechanism of Hin-DNA interaction, the activation of the Hin-DNA cleavage reaction, the nature of the interaction of Hin with the enhancer complex and the mechanism involved in Hin-DNA inversion. We will use extensive mutagenesis, studies of invivo function and in vitro reconstitution with modified protein and DNA sites to understand how the recombinase and enhancer function during the course of the reaction.
