Action at a distance in Mu DNA transposition: an enhancer‐like element is the site of action of supercoiling relief activity by integration host factor (IHF).

The first committed step in the in vitro strand transfer reaction of a mini‐Mu donor molecule is the formation of a Type 1 complex in which the Mu ends are held together in a non‐covalent protein‐DNA complex. Efficient formation of this complex at high levels of donor supercoiling (sigma approximately ‐0.06) requires the Mu A and Escherichia coli HU proteins. At in vivo levels of supercoiling, efficient reaction also requires E. coli …