FIG. 5.

ERα transcriptional activity with chromatin templates is impaired in Mediator-depleted nuclear extracts. (A) Analysis of ERα-dependent transcription with chromatin templates by using control and Mediator-depleted HNEs. The 2ERE-pS2 (pS2 promoter) and pERE (E4 promoter) plasmid templates were assembled into chromatin in the presence of purified recombinant ERα, E₂, and p300 as indicated. The chromatin samples were subjected to in vitro transcription analysis, and the resulting RNA products were analyzed by primer extension. The relative transcription for each promoter is indicated. (B) Summary of multiple experiments like those in panel A showing the effects of Mediator depletion on activated transcription by ERα with the human pS2 and adenovirus E4 promoters. The data are plotted as fold activation over basal to account for the modest effects that Mediator depletion has on basal transcription (Fig. 4). Each bar represents the mean + the standard error from three or more separate determinations.