GAG-GAG INTERACTIONS IN THE C-TERMINAL DOMAIN OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 P24 CAPSID ANTIGEN ARE ESSENTIAL FOR GAG PARTICLE ASSEMBLY

Seven internal deletions within the p24 domain of the human immunodefi ciency virus type 1 Gag precursor have been assessed for their effect on Gag particle formation following their expression using recombinant baculoviruses. In addition, each deleted molecule was assessed for it s ability to bind soluble p24 antigen in vitro. The mutants fell into three different phenotypic groups: (i) three mutants that had no effec t on either p24 binding or Gag particle assembly, (ii) three mutants t hat abolished both features and (iii) one mutant that bound p24 in vit ro but failed to assemble particles. Mutations that abolished both in vitro p24 binding and particle assembly mapped to the C terminus of p2 4 confirming this region as critical for virion assembly. We suggest t hat the division of virion assembly into at least two distinct phases and suggest a model in which the critical sequences mapped to date are combined with available structural information.