Abstract
Human immunodeficiency virus type 1 nucleocapsid (NC) basic residues presumably contribute to virus assembly via RNA, which serves as a scaffold for Gag–Gag interaction during particle assembly. To determine whether NC basic residues play a role in Gag cleavage (thereby impacting virus assembly), Gag processing efficiency and virus particle production were analyzed for an HIV-1 mutant NC15A, with alanine serving as a substitute for all NC basic residues. Results indicate that NC15A significantly impaired virus maturation in addition to significantly affecting Gag membrane binding and assembly. Interestingly, removal of the matrix (MA) central globular domain ameliorated the NC15A assembly and processing defects, likely through enhancement of Gag multimerization and membrane binding capacities.
Highlights
In most retroviruses, Gag precursor polypeptide expression is sufficient for mediating virus particle assembly [1]
We found that blocking NC-RNA association via the alanine replacement of all NC basic residues (NC15A) reduced Gag cleavage efficiency and significantly impaired Gag assembly
The secondary antibody was a sheep anti-mouse horseradish peroxidase (HRP)-conjugated antibody diluted at 1:15,000
Summary
Gag precursor polypeptide expression is sufficient for mediating virus particle assembly [1]. During or soon after virus budding, HIV-1 Gag precursor Pr55 is cleaved by viral protease (PR) into matrix (MA; p17), capsid (CA; p24), nucleocapsid (NC; p7) and p6 domains [1,2]. This PR-mediated virus maturation process is essential for acquiring viral infectivity [3,4,5,6]. Maintenance of a low PR-associated Gag-Pol expression level is considered critical, since the artificial overexpression of Gag-Pol or PR triggers reduced
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