Requirement of CREB, TORCs and p300/CBP for Pak3-augmented activation of HTLV-1 LTR by Tax. Escalating amounts of A-CREB (A), CRTC1M1 (B), and E1A-12S (C) plasmids were transfected into HeLa cells. Dual luciferase assays were carried out as in Figure 1. Numbers at the top of the error bars indicate fold activation. Expression of A-CREB, CRTC1M1 and E1A-12S was verified by Western blotting with mouse anti-Flag, rabbit anti-Gal4 and rabbit anti-E1A antibodies (insets). n.s.: non-specific proteins reactive with anti-Gal4.