Fig. 4.

Endolysosome but not cytosolic iron chelators enhanced Tat-mediated HIV-1 LTR transactivation. A U87MG cells stably transfected with a luciferase gene under the control of the Tat responsive HIV-1 LTR promoter were incubated for 48 h with the endolysosome-specific iron chelators deferoxamine (DFO) or 2–2 bipyridyl at concentrations ranging from 0.25 to 100 μM and HIV-1 Tat protein (2 μg/ml) in the presence of chloroquine (CQ, 100 μM). Luciferase activity (percent of control) was significantly increased by DFO starting at concentrations of 1.0 μM (left panel) and by 2–2 bipyridyl starting at concentrations of 50 μM (right panel). B No statistically significant effects on Tat-mediated HIV-1 LTR transactivation were observed when U87MG cells were incubated for 48 h with the cytosolic iron chelators deferiprone or deferasirox at concentrations ranging from 2.5 to 100 μM in the presence of Tat protein (2 μg/ml) and CQ (100 μM). (n = 3; *p < 0.05; **p < 0.01, ***p < 0.001, ****p < 0.0001)