Domains upstream of the protease (PR) in human immunodeficiency virus type 1 Gag-Pol influence PR autoprocessing.

A critical step in the formation of infectious retroviral particles is the activation of the virally encoded protease (PR) and its release from the Gag-Pol precursor polyprotein. To identify factors that influence this step, the maturation of human immunodeficiency virus type 1 PR from various Gag-PR polyproteins was assayed in vitro by a using rabbit reticulocyte lysate as a coupled transcription-translation-autoprocessing system. Highly efficient autoprocessing was detected with polyproteins containing the viral nucleocapsid (NC) domain. In contrast, polyproteins consisting of only p6 and PR domains or containing a truncated NC domain exhibited no autoprocessing activity. Experiments designed to test the dimerization capability of short PR polyproteins revealed that precursors containing the NC domain exhibited very efficient homotypic protein-protein interactions while PR precursors consisting of only p6 and PR did not interact efficiently. The strong correlation between autoprocessing activity and PR polyprotein precursor dimerization suggests that NC and p6* domains play a role in PR activation by influencing the dimerization of the PR domain in the precursor.