Figure 1. Schematic representation of HIV-1 Env-mediated cell-cell fusion assay. HEK293T
cell was co-transfected with two recombinant plasmids, pcHXB3Env and pcDNA3.1Tat101-
FLAG, in order to express HIV-1 Env proteins on the cell surface and produce regulatory Tat
protein, respectively. HeLa T4+ cell was transfected with pTruLTRGFP to harbor LTRdriven
copGFP. Cell fusion facilitated content mixing that allowed Tat binding to the HIV-1
LTR, resulting in LTR-driven copGFP expression in fused cell. The production of copGFP
was then quantified by determining of green fluorescent signal. In the presence of fusion
inhibitor, cell-cell fusion was inhibited which displayed as low-background of copGFP
intensity.