BIOCHEMICAL-MECHANISM OF HIV-1 VPR FUNCTION - OLIGOMERIZATION MEDIATED BY THE N-TERMINAL DOMAIN

The human immunodeficiency virus, type 1 (HIV-1) genome encodes a 15-k Da accessory gene product, Vpr, that is essential for virus replicatio n in primary monocytes/macrophages. Being present in the virion, Vpr i s believed to function in the early phases of HIV-1 replication, inclu ding nuclear migration of the pre-integration complex and/or transcrip tion of the provirus genome. By gel filtration analysis of highly puri fied Vpr protein and its mutants, we demonstrate that HIV-1 Vpr exists as an oligomer, The N-terminal domain of Vpr (amino acids (aa) 1-42) is sufficient for oligomerization; however deletion of aa 36-76 from V pr disrupts oligomerization, suggesting that aa 36-42 are critical for Vpr oligomerization, As a result of Vpr oligomerization, basic aa res idues within Vpr aa 1-73 are highly resistant to trypsin digestion, wh ile those within Vpr aa 74-96 are easily accessible, Mutations within the leucine-/isoleucine-rich domain (aa 60-81), which was previously i dentified to be involved in Vpr interaction with a host cellular prote in, rendered Arg(62) more susceptible to trypsin digestion, Thus, the Vpr oligomeric structure must be extended into this domain. These resu lts suggest a novel feature of HIV-1 Vpr that may be important for its functions.