FIG. 2.

Individual fractions support accurate transcription initiation following sedimentation of DE350 fractions through glycerol gradients. Gradients (11.5 ml) were fractionated into 30 fractions and tested for total Pol I activity on nicked calf thymus DNA (top). Reactions were performed in triplicate, and the mean values for each fraction were plotted. Error bars represent the standard errors of the means. Fractions were also tested for their ability to program accurate, promoter-dependent Pol I transcription (autoradiogram at bottom). Transcripts were detected by S1 nuclease protection. Fraction 20 represented the peak in both assays.