Fig. S1. Detection of fluorescently tagged mRNPs in transcriptionally activated cells. (A) An example of a U2OS cell containing the integrated gene which was co-transfected by electroporation with the RFP-lac repressor, YFP-MS2 and pTet-On plasmids. Three hours post-transfection doxycycline was added to the medium. The cells were then fixed three hours post-induction. The open gene locus was detectable with the RFP-lac repressor protein, simultaneously with (B) YFP-MS2 nuclear particles, (C) YFP-MS2 cytoplasmic particles (longer exposure of the same cell) and (D) cytoplasmic CFP-peroxisomes. Bar = 5 µm.