Uracil DNA glycosylase specifically interacts with Vpr of both human immunodeficiency virus type 1 and simian immunodeficiency virus of sooty mangabeys, but binding does not correlate with cell cycle arrest.

The Vpr protein encoded by human immunodeficiency virus type 1 (HIV-1) is important for growth of virus in macrophages and prevents infected cells from passing into mitosis (G2 arrest). The cellular target for these functions is not known, but Vpr of HIV-1 and the related Vpr from simian immunodeficiency virus of sooty mangabeys (SIV(SM)) bind the DNA repair enzyme UNG, while the Vpx protein of SIV(SM) does not. Nonetheless, a mutational analysis of Vpr showed that binding to UNG is neither necessary nor sufficient for the effect of Vpr on the cell cycle.