IRF-8 activation of transcription through the IECS. (A) Diagram of the SIRV reporter driven by the IECS. (B) Activation of transcription through the IECS by IRF-8/ER. Tot2 cells were transduced with SIRVIECS-Ld40-GFP or SIRV-IECS-Ld40-GFP, and then with MSCV-ER or MSCV–IRF-8/ER. Cells were either left untreated or were treated with 1 μM β-estradiol (Est) for 13 hours. Values represent fold changes in MFI induced by estradiol treatment. (C) Activation of transcription through the IECS by wild-type IRF-8. Tot2 cells were transduced with SIRV-Ld40-GFP or SIRV-IECS-Ld40-GFP and then with empty MSCV or MSCV–IRF-8. Cells were analyzed on day 2 after transduction of MSCVs. Values represent fold changes in MFI induced by IRF-8.