Marno, K. M. | Search bioRxiv

bioRxiv2026

HIV-1 Vpr counteracts TASOR restriction to promote infection prior to integration

HIV-1 is challenged by many intrinsic antiviral factors including APOBEC3G, Tetherin/BST-2 and SERINC5 which are overcome by viral accessory proteins Vif, Vpu and Nef respectively. HIV-1 Vpr has multiple proposed cellular targets including REAF, previously shown by us to restrict early after virus entry, but its function is incompletely understood. TASOR is a component of HuSH, an epigenetic silencing complex which inhibits expression of HIV-1 and is overcome by HIV-2/SIV Vpx. We report that TASOR, in addition to silencing integrated provirus, inhibits viral replication prior to integration during reverse transcription. TASOR impairs viral replication in primary macrophages and restriction of a primary isolate is also shown. The restriction to replication is overcome by HIV-1 Vpr which induces TASOR degradation concomitant with reverse transcription. Using Vpr mutants Q65R and F34I we show that interaction with the CRL4-DCAF1 E3 ligase and nuclear localisation are required for Vpr to mitigate TASOR. The pre and post integration mechanism of Vpr mediated TASOR mitigation is genetically segregated using cell cycle Vpr mutant R80A. TASOR depletion induces cells to accumulate in G2/M and arrested cells are more susceptible to HIV-1. Understanding the mechanistic details of pathogen-host interactions is critical for the design of effective anti-HIV/AIDS therapeutics.

immunology↗

bioRxiv2018

HIV-1 Vpr accessory protein interacts with REAF and mitigates its associated anti-viral activity.

The Human Immunodeficiency Virus type 1 (HIV-1) accessory protein Vpr enhances viral replication in both macrophages and in cycling T cells to a lesser extent. Virion packaged Vpr is released in target cells shortly after entry, suggesting its requirement in the early phase of infection. Previously, we described REAF (RNA-associated Early-stage Antiviral Factor, RPRD2), a constitutively expressed protein that potently restricts HIV replication at or during reverse transcription. Here, we show that a virus without intact vpr is more highly restricted by REAF and, using delivery by VLPs, that Vpr alone is sufficient for REAF degradation in primary macrophages. REAF is more highly expressed in macrophages than in cycling T cells and we detect, by co-immunoprecipitation assay, an interaction between Vpr protein and endogenous REAF. Vpr acts very quickly during the early phase of replication and induces the degradation of REAF within 30 minutes of viral entry. Using Vpr F34I and Q65R viral mutants, we show that nuclear localisation and interaction with cullin4A-DBB1 (DCAF1) E3 ubiquitin ligase is required for REAF degradation by Vpr. In response to infection, cells upregulate REAF levels. This response is curtailed in the presence of Vpr. These findings support the hypothesis that Vpr induces the degradation of a factor, REAF, which impedes HIV infection in macrophages.\n\nImportanceFor at least 30 years, it has been known that HIV-1 Vpr, a protein carried in the virion, is important for efficient infection of primary macrophages. Vpr is also a determinant of the pathogenic effects of HIV-1 in vivo. A number of cellular proteins that interact with Vpr have been identified. So far, it has not been possible to associate these proteins with altered viral replication in macrophages, or to explain why Vpr is carried in the virus particle. Here we show that Vpr mitigates the antiviral effects of REAF, a protein highly expressed in primary macrophages and one which inhibits virus replication early during reverse transcription. REAF is degraded by Vpr within 30 minutes of virus entry, in a manner dependent on the nuclear localization of Vpr and its interaction with the cells protein degradation machinery.

microbiology↗