Characterization of human immunodeficiency virus type 1 Pr160 gag-pol mutants with truncations downstream of the protease domain.

We have constructed a series of HIV-1 Gag-pol mutants by progressive deletion of the pol sequence downstream of the viral protease (PR) domain. Effects of the truncation mutations on virus particle production and Gag particle processing were analyzed. Analysis indicated that removal of the integrase (IN) domain had no major effect on the efficiency of particle processing, but resulted in a marked reduction in virus particle budding. Deletion of both the IN and RNase H domains, however, restored the production of virus particles to wild-type level. The proteolytic processing of virus particle was significantly impaired when the p51RT domain was truncated. All of the truncated Gag-pol proteins could be incorporated into virus particles and demonstrated an immunofluorescence staining pattern similar to that of the wild type (wt). Our data are consistent with the proposal that signals for directing the Gag-pol transport and particle incorporation are determined by its N-terminal Gag domain. Truncated Gag-pol retaining an intact p51RT was able to complement a PR-defective mutant to produce infectious pseudotyped virions, with a virus titer 20-70% of that of wt. Pseudotyped virions produced by the Gag-pol lacking an intact p51RT were noninfectious or poorly infectious. This suggests that an intact p51RT domain is required for the Gag-pol to mediate production of mature infectious virus particles in trans.