Figure 2.

Time course of PR mRNA transcription rate after E₂ treatment. Rat1+ER cells were treated with E₂ (10 nM) for the indicated times and the nuclei were isolated. Nuclei were incubated with ³²P-UTP and other ribonucleotides to label nascent transcripts from engaged RNA polymerases. The steady-state number of RNA polymerases, i.e., transcription rate, was determined by hybridizing ³²P-labeled primary transcripts to the plasmids immobilized on the membrane. (A) One representative nuclear run-on blot is shown with each plasmid designated. For detailed description of plasmids, see Materials and Methods. Time periods for E₂ treatments are labeled at the top. (B) The blots were quantified by PhosphorImager. PR gene transcription rates were normalized to those of CHOB after subtracting backgrounds. The results were expressed as fold-changes relative to the control value. The quantified results represent an average of four independent experiments and are shown on the right, vertical axis. The E₂–ER level was measured by whole cell uptake using the same E₂ concentration, as shown in Fig. 3A. The data are overlaid on the left, y axis as a dashed line.