Effects of Neighboring DNA homopolymers on the biochemical and physical properties of the Escherichia coli lactose promoter. II. In vitro transcription analyses.

Transcription studies were conducted on the primary promoter (which initiates at +1) of lac wild type (wt) and UV5 that had insertions of poly(dA).poly(dT) or poly(dG).poly(dC) in their -60 region. This series of recombinant DNAs was designed to study systematically the effect of neighboring DNA sequences on the lac promoter. Investigations using linear templates showed that wild type expression was enhanced by the poly(dA).poly(dT) insertion, whereas UV5 activity was not affected by this polymer. Neither the wt nor the UV5 promoter was influenced by the presence of poly(dG).poly(dC). Quantitation of abortive transcripts from supercoiled templates showed that the influence of the polymers on promoter activity was small. Comparative studies of the primary promoter with a secondary promoter (which initiates near -22), activated by 25% glycerol, were performed.