ROLE OF THE CONSERVED DIPEPTIDE GLY75 AND CYS76 ON HIV-1 VPR FUNCTION

Vpr is one of the accessory proteins encoded by the HIV-1 genome. Seve ral interesting features associated with Vpr include incorporation int o virus particles, ability to oligomerize, localization in the nucleus , and positive effect on virus production and replication. In order to understand the structure-function relationship of Vpr, we have analyz ed the role of the Gly75 and Cys76 (GC) residues which are highly cons erved in HIV-1 Vpr and in Vpr and Vpx of HIV-2/SIV. We have generated several substitution mutants involving this dipeptide and have evaluat ed for expression, stability, nuclear localization, and virion incorpo ration of Vpr. Our data demonstrate that the GC residues are not essen tial for virion incorporation and nuclear localization of Vpr. Serine substitution for Cys, however, restricted the localization of Vpr in t he cytoplasm without affecting the Gag-directed incorporation of Vpr i nto virus-like particles. Interestingly, the cysteine-substituted muta nts showed altered stability in comparison to the wild type, and subst itution mutants for glycine showed minimal effect on stability. These results indicate that the glycine and cysteine do not play a role in n uclear localization or virion incorporation properties of Vpr and furt her suggest that these two functions of Vpr may not be interdependent. (C) 1995 Academic Press, Inc.