Influence of MA internal sequences, but not of the myristylated N-terminus sequence, on the budding site of HIV-1 Gag protein.

HIV-1 Gag protein intracellular transport and budding was investigated by altering the sequence of the MA domain, which directly bears an essential N-terminal myristyl adduct and forms the viral matrix after Gag proteolysis in mature virions. We found that removal of a substantial MA internal segment did not abolish the assembly and budding of Gag particles, but rather diverted these events to intracellular cisternae. The internally deleted Gag was further modified by substituting either of two heterologous myristylated N-termini for the natural one: amino acids 1-12 from v-Src oncoprotein (for which a membrane-bound intracellular receptor has been postulated), or amino acids 1-12 from Poliovirus polyprotein (for which no membrane-targeting function has been demonstrated). Both Src-Gag and Polio-Gag chimerae exhibited transport and processing characteristics similar to those of the MA-deleted Gag. These results are discussed with respect to the possible transport pathway of HIV-1 Gag.