FIG. 1.
Packaging of UDG into viral particles is independent of the presence of Vpr. (a) Cell-free supernatants from wild-type and Vpr-defective virus-infected H9 T cells were treated with subtilisin, pelleted by ultracentrifugation, and monitored for equal amounts of p24. The viral pellet was solubilized in sample buffer, separated on an SDS–12% polyacrylamide gel, and analyzed by Western blotting for the presence of Vpr and Gag products with ECL reagents. (b) Virions were purified on a linear 20 to 60% sucrose density gradient. Aliquots of each gradient fraction were analyzed for reverse transcriptase activity (upper panel). Virus particles in each gradient fraction were pelleted and solubilized in sample buffer, and viral proteins were separated by SDS-PAGE and analyzed by Western blotting for the presence of UDG and Gag products (lower panel).