Primate Lentiviral Vpx Commandeers DDB1 to Counteract a Macrophage Restriction

Abstract

Primate lentiviruses encode four “accessory proteins” including Vif, Vpu, Nef, and Vpr/Vpx. Vif and Vpu counteract the antiviral effects of cellular restrictions to early and late steps in the viral replication cycle. We present evidence that the Vpx proteins of HIV-2/SIVSM promote virus infection by antagonizing an antiviral restriction in macrophages. Fusion of macrophages in which Vpx was essential for virus infection, with COS cells in which Vpx was dispensable for virus infection, generated heterokaryons that supported infection by wild-type SIV but not Vpx-deleted SIV. The restriction potently antagonized infection of macrophages by HIV-1, and expression of Vpx in macrophages in trans overcame the restriction to HIV-1 and SIV infection. Vpx was ubiquitylated and both ubiquitylation and the proteasome regulated the activity of Vpx. The ability of Vpx to counteract the restriction to HIV-1 and SIV infection was dependent upon the HIV-1 Vpr interacting protein, damaged DNA binding protein 1 (DDB1), and DDB1 partially substituted for Vpx when fused to Vpr. Our results indicate that macrophage harbor a potent antiviral restriction and that primate lentiviruses have evolved Vpx to counteract this restriction.

Interleukin-2 Inhibits HIV-1 Replication in Some Human T Cell Lymphotrophic Virus-1-infected Cell Lines via the Induction and Incorporation of APOBEC3G into the Virion

“…In the HIV binding assay, MT-2 cells were pretreated with or without 20 units/ml of IL-2 for 4 days, and the cells were incubated with DNase-treated HIV-1 at 4°C for 2 h, followed by washing with ice-cold PBS. HIV-1 infection or binding was evaluated by measuring the products of viral cDNA synthesis at 24 and 48 h postinfection, as described previously (45). Copy numbers were normalized to total cell numbers determined by real time PCR using CCR5-specific primers (11,46).…”

How Samhd1 changes our view of viral restriction

“…Most accessory proteins are instrumental in the counteraction of cellular restriction factors -indeed A3G as well as BST-2 and SAMHD1 were identified in attempts to decipher the function of viral auxiliary proteins (Vif, Vpu, Vpx and Vpr). In elegant experiments in which heterokaryons were generated from permissive and non-permissive cells, it was evident that the block in viral replication was caused by the presence of a dominant negative cellular factor that directly hindered the replication cycle [19][20][21]. The exception to this rule is TRIM5α, which is not counteracted by a viral accessory protein.…”

SIVMAC Vpx improves the transduction of dendritic cells with nonintegrative HIV-1-derived vectors

“…Indeed, Vpx has been reported to associate with this complex either via an adaptor protein, the DDB1-(damaged DNA-binding protein 1) and CUL4-associated factor 1, or via its structural component, the DDB1. 19,20 Removal of these factors by small interfering RNAs impaired the functionality of Vpx, suggesting that Vpx may target a cellular factor to this E3-ubiquitin ligase complex and induce its degradation. This function would be required to remove an antiviral restriction present in DCs, thereby exerting a protective effect on viral nucleoprotein complexes.…”