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We have generated a series of 3′ deletions of a cloned copy of the bacteriophage Mu transposase (A) gene. The corresponding truncated proteins, expressed under the control of the λ PI promoter, were analysed in vivo for their capacity to complement a super-infecting MuAam phage, both for lytic growth and lysogeny, and for their effect on growth of wild-type Mu following infection or induction of a lysogen. Using crude cell extracts, we have also examined binding properties of these proteins to the ends of Mu. The results allow us to further define regions of the protein important in replicative transposition, establishment of lysogeny and DNA binding. [ABSTRACT FROM AUTHOR]

We show, using gel retardation, that crude Escherichia coli cell extracts contain a protein which binds specifically to DNA fragments carrying either end of the phage Mu genome. We have identified this protein as Fis, a factor involved in several site-specific recombinational switches. Furthermore, we show that induction of a Mucts62 prophage in a fis lysogen occurs at a lower temperature than that of a wild-type strain, and that spontaneous induction of Mucfs62 is increased in the fis mutant. DNasel footprinting using either crude extracts or purified Fis indicate that binding on the left end of Mu occurs at a site which overlaps a weak transposase binding site. Thus, Fis may modulate Mu growth by influencing the binding of transposase, or other proteins, to the transposase binding site(s), in a way similar to its influence on Xis binding in phage λ. [ABSTRACT FROM AUTHOR]