INHIBITION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 PARTICLE FORMATION BY ALTERATIONS OF DEFINED AMINO-ACIDS WITHIN THE C-TERMINUS OF THE CAPSID PROTEIN

In previous studies, we demonstrated that the substitution of amino ac id triplets for alanines in the carboxy-terminal portion (amino acids 341-352: ATL EEM MTA CQC) of the capsid protein domain (p24) of human immunodeficiency virus type 1 (HIV-1) partly led to an inhibitory effe ct on the capacity to form virus-like particles (VLPs). In these exper iments, the uncleaved Pr55(gag) precursor protein was expressed by rec ombinant vaccinia viruses. We have now investigated the effects of the se mutations with respect to a replication-competent Hf-provirus syste m, Substitution of amino acids 344-346 (EEM) for alanines, which was p reviously shown to lead to an inhibition of VLP formation, completely blocked assembly and release of HIV. A substantial reduction of HIV sy nthesis was also observed in the proviral system after exchange of ami no acids 347-348 [MT(A)] which, in contrast, was formerly shown to res ult in an increased formation of VLPs. Western blot analysis of lysate s of cells transfected with these mutated proviral constructs revealed an abnormal intracellular processing pattern of the Pr55(gag) precurs or molecules. Further analyses suggest a structural aberration of thes e altered polyproteins as the basis for the observed block of virus fo rmation.