Fig. 1. Inhibition of RNA polymerase II activity by DRB or AMD treatment. (A) Integrated fluorescent intensity of HCMV IE transcripts accumulated in the nuclear foci relative to the integration site. Addition of either RNA polymerase II inhibitor resulted in a rapid decrease (half time 2 minutes) in the amount of HCMV IE transcripts accumulated in nuclear foci. (B) Integrated fluorescent intensity of HCMV IE transcripts dispersed through the nucleoplasm relative to negative nuclei. The amount of HCMV IE mRNAs in the remainder of the nucleoplasm decreased at a much slower rate (half time 10 minutes). (C) CSLM images of cells at different times after RNA polymerase II inactivation. After induction of the HCMV IE gene expression by cycloheximide, transcripts were present in nuclear foci and also dispersed throughout the nucleoplasm. These images demonstrate the decrease in the amount of transcripts in the nuclear foci and in the nucleoplasm at different intervals after addition of a RNA polymerase II inhibitor. At all times, HCMV IE transcripts were observed in the cytoplasm.