Comparison of the expression levels of viral proteins from pNL4-3 and pΔR. 293T cells were transfected with pcDNA3 (left lane in each blot), pNL4-3 (middle lane), or pΔR (right lane). Virions were pelleted through sucrose cushions and examined by Western blotting using anti-CA (top left), anti-MA (top middle), anti-NC (top right), anti-gp41 (lower left), or anti-RT (lower right) antibodies. The variant RT proteins expressed from pΔR travel slightly faster than the wild-type RT proteins (compare lane 15 to lane 14). HIV-1-specific proteins are identified on the right side of each panel.