Effects of reduced gag cleavage efficiency on HIV-1 Gag-Pol package

Abstract

Abstract Background HIV-1 pol, which encodes enzymes required for virus replication, is initially translated as a Gag-Pol fusion protein. Gag-Pol is incorporated into virions via interactions with Gag precursor Pr55 gag . Protease (PR) embedded in Gag-Pol mediates the proteolytic processing of both Pr55gag and Gag-Pol during or soon after virus particle release from cells. Since efficient Gag-Pol viral incorporation depends on interaction with Pr55 gag via its N-terminal Gag domain, the prevention of premature Gag cleavage may alleviate Gag-Pol packaging deficiencies associated with cleavage enhancement from PR. Results We engineered PR cleavage-blocking Gag mutations with the potential to significantly reduce Gag processing efficiency. Such mutations may mitigate the negative effects of enhanced PR activation on virus assembly and Gag-Pol packaging due to an RT dimerization enhancer or leucine zipper dimerization motif. When co-expressed with Pr55 gag , we noted that enhanced PR activation resulted in reduced Gag-Pol cis or trans incorporation into Pr55 gag particles, regardless of whether or not Gag cleavage sites within Gag-Pol were blocked. Conclusions Our data suggest that the amount of HIV-1 Gag-Pol or Pol viral incorporation is largely dependent on virus particle production, and that cleavage blocking in the Gag-Pol N-terminal Gag domain does not exert significant impacts on Pol packaging.

Keywords

• HIV-1
• Protease
• Gag
• Gag-Pol
• Gag cleavage
• Virus assembly