FIG. 1.

The PPPY motif is responsible for virus export. (A) Genetic map of HTLV-1 showing the major open reading frames. The processed peptides of Gag are indicated in the expanded view of the Gag precursor protein. The late assembly motif and its surrounding sequence are shown; below, the mutations used in this study are indicated. pX1MT-PTAP/P3Y and pX1MT-PTAP/P3G contain an extra proline codon. We also tested the construct without the additional proline and saw no difference (data not shown). (B) Western blots of proteins from viral pellets (left) and cellular extracts (right) probed with a mouse monoclonal anti-MA antibody followed by a horseradish peroxidase-conjugated anti-mouse antibody. Blots were developed with ECL⁺ and exposed to X-ray film. Pellets and extracts were obtained from 293T cell cultures transiently transfected with pX1MT (lanes 1), pX1MT-P3G (lanes 2), pX1MT-A3P (lanes 3), and pX1MT-P3A/A3P (lanes 4). The positions of molecular weight markers are given on the left. (C) ELISA determination of the percentages of MA in the supernatant compared to the total MA in the culture. The results of three experiments are summarized. Sample designations are the same as for panel B. (D) Relative total amounts of MA in each culture expressed as percentages of MA expressed by the pX1MT construct. The results of three experiments are summarized. Sample designations are the same as for panel B. Error bars in panels C and D indicate standard errors.