Discrete promoter elements affect specific properties of RNA polymerase II transcription complexes

The frequency of transcription initiation at specific RNA polymerase II promoters is, in many cases, related to the ability of the promoter to recruit the transcription machinery to a specific site. However, there may also be functional differences in the properties of assembled transcription complexes that are promoter-specific or regulator-dependent and affect their activity. Transcription complexes formed on variants of the adenovirus major late (AdML) promoter were found to differ in several ways. Mutations in the initiator element increased the sarkosyl sensitivity of the rate of elongation and decreased the rate of early steps in initiation as revealed by a sarkosyl challenge assay that exploited the resistance of RNA synthesis to high concentrations of sarkosyl after formation of one or two phospho-diester bonds. Similar, but clearly distinct, effects were also observed after deletion of the binding site for upstream stimulatory factor from the AdML promoter. In contrast, deletion of binding sites for nuclear factor 1 and Oct-1, as well as mutations in the recognition sequence for initiation site binding protein, were without apparent effect on transcription complexes on templates containing the mouse mammary tumor virus promoter.