Figure 4.

Confocal microscopy of cells co-expressing HIV-1 Gag, Env and SR-protein. Panel A: 293T cells expressing HIV-1 pNL4.3 were subjected to immuno-staining using anti-Map17 (green staining) and anti-Env gp120 (red staining) antibodies and staining was viewed by confocal microscopy as described in methods. Most if not all cells expressed Gag and Env but only partial colocalization was seen (merge picture). Right panel corresponds to the same cells viewed by phase contrast microscopy. Panel B: same as in A except that His tagged-ASF/SF2 SR protein was overexpressed by DNA transfection with about 75% transfection efficiency (see methods). ASF/SF2 protein is localized in the nucleus (blue staining) and its overexpression caused a drastic reduction of Env level while Gag remained well expressed in agreement with the western blot data (Figure 3) but with an heterogenous pattern (first panel). Panel C: same as in A except that His tagged-SC35 SR protein was overexpressed by DNA transfection with about 75% transfection efficiency (see methods). SC35 protein (nuclear blue staining) overexpression caused a reduction of Env level while Gag was still highly expressed in agreement with the western blot data (Figure 2). Note that in all cases examined here (anti-Map17; green staining in panel A to C) Gag was found to accumulate at the plasma membrane and in intracellular compartments corresponding to vesicles [42] (Muriaux et al., unpublished data).