The influence of ribonucleoside triphosphates, and other factors, on the formation of very-salt-stable RNA-polymerase . su+III-tRNA(tRNATyr)-promoter complexes.

The formation of a stable RNA-polymerase . su+III-tRNA-promoter complex was found to require sigma factor and the incorporation of ribonucleoside triphosphates which match the 5' sequence of the su+III tRNA transcript. This complex, stable to at least 2 M KCl, can be retained on a Millipore filter. Its formation closely parallels the extent of transcription obtained from the su+III tRNA promoter in response both to increasing ionic strength and to temperature during incubation of RNA polymerase with the DNA. The RNA-polymerase . DNA complex retained during this assay therefore appears to relate directly to that formed during promoter-directed transcription. The formation of RNA-polymerase . su+III-tRNA-promoter complexes is sensitive to the presence of ppGpp.