Silencing of STAT5Δ expression enhances GM-CSF stimulated HIV production in U1 cells. (A) Western blot analysis of U1 cells electroporated with either control or STAT5 siRNA. Twenty-four hours after siRNA electroporation, U1 cells were stimulated with GM-CSF and their WCE were prepared at the indicated time points. Membranes were hybridized with anti-STAT5 mAb (upper panel), anti-phospho-STAT5 mAb (middle panel), and anti-α-actin Abs (lower panel). (B) U1 cells were electroporated with STAT5 or control siRNA and 24 hours later they were either left unstimulated (Nil) or were stimulated with GM-CSF (20 ng/mL). HIV-1 production was measured by RT activity in culture supernatants. The results shown were obtained in a single experiment representative of five independently performed in triplicate cultures (mean ± standard deviation).