Fig. (2) STAT5–P, but not STAT5, activates the subtype B HIV-1 LTR. 293T cells were co-transfected with equal amounts of a β-casein responsive firefly luc reporter construct (upper panel) and either an empty vector or vectors expressing STAT5 or STAT5-P. Similar constructs were transfected in 293T-LTR-GFP cells (see Material & Methods). The results represent the mean ± SEM of 3 independent experiments.