Construction and properties of a ColE1::Tn3-cos lambda plasmid for determining RNA polymerase binding sites on ColE1 and Tn3.

To determine the location of the RNA polymerase binding sites on the ColE1 plasmid and Tn3 transposon, a special hybrid ColE1::Tn3-cos lambda molecule was constructed which contains the left arm of phage lambda DNA and the right lambda terminal fragment. This permits orienting ColE1 molecules, since the RNA polymerase binding pattern of these two lambda fragments are known to be distinct. ColE1 DNA contains seven binding sites and Tn3 binds three RNA polymerases, with some of the latter probably involved in the expression of the transposition of functions of this transposon. The relationship of these sites to the positions and orientations of known promoters, transcripts, genes and functions is discussed.