FIG. 7.

ESCRT proteins are present in enveloped HSV-1 virions. HSV-1 stain StH2 that had been purified on a 5 to 15% Ficoll continuous gradient was incubated in the presence or absence of 1% Triton X-100, together with the presence or absence of trypsin at 37°C for 1 h. The reaction was stopped by adding protease inhibitor cocktail (Roche). Any proteins incorporated into the virus particle would be protected from protease treatment by the virus envelope in the absence of detergent, and proteins that were not incorporated into the virus particle and so present outside the virus envelope would be sensitive to protease treatment irrespective of the presence of detergent. All samples were analyzed by Western blotting for the presence of the envelope protein gD, the tegument protein VP16, and cellular ESCRT proteins. Totals of 4 × 10⁷ PFU and 4 × 10⁶ PFU per lane, respectively, were loaded for the detection of cellular proteins and viral proteins.