Separation and characterization of factors mediating accurate transcription by RNA polymerase II.

A whole cell extract of HeLa cells was resolved through two successive chromatographic steps using an extension of the procedure of Matsui et al. (Matsui, T., Segall, J., Weil, P. A., and Roeder, R. G. (1980) J. Biol. Chem. 255, 11992-11996). RNA polymerase II and three of the resulting fractions were necessary and sufficient for accurate transcription of the adenovirus major late promoter. This accurate transcription was quantitated as a function of each of the required fractions, polymerase, and DNA. A linear range of response was observed in each case. Using the linear ranges for assay, it was possible to calculate net purifications and yields for each of the required transcriptional activities after chromatography. These activities were each shown to sediment with a distinct peak on sucrose gradients. The effects of variations in salt concentration, magnesium concentration, temperature, and reaction time were determined. High resolution analysis of runoff transcripts showed that the reconstituted system initiated transcription precisely at the adenovirus major late and early region IV promoters.