Our objective is understanding molecular mechanisms of transposition of mobiles genetic elements. We study bacteriophage Mu, as mechanisms used in Mu transposition are highly analogous to those of other mobile genetic elements, prokaryotic and eukaryotic. Thus unique properties of Mu as a lysogenic virus and a transposon allow use of in vivo biochemical studies which are difficult or impossible in systems with low frequency of transposition. During the present grant period, we will focus on understanding the role of a novel transposition enhancer (CEN), located in the center of the Mu genome, which contains a strong DNA gyrase binding site. We will test models for use of CEN-like enhancers in other systems. CEN is the clearest example presently available of a gyrase binding site with a specific function. Study of its mechanism of action should help in understanding not only the role of gyrase in transposition, but also in organization of large DNA structures such as the prokaryotes nucleoid.
