APOBEC3G is a cytidine deaminase that limits the replication of many retroviruses. This antiviral host factor is packaged into retrovirus particles, where it targets single-stranded DNA generated ...during reverse transcription and induces up to 2% of G-to-A mutations, which are lethal for the HIV-1 provirus. Vif protein counteracts this antiviral factor by decreasing its packaging into lentivirus particles. Here, we demonstrate that Nedd4-1, an HECT E3 ubiquitin ligase, interacts with APOBEC3G, through its WW2 and WW3 domains. As a result of this interaction, APOBEC3G undergoes post-translational modification by addition of ubiquitin moieties. Accordingly, we demonstrate that the dominant negative Nedd4-1 C/S form prevents APOBEC3G ubiquitination. Moreover, the packaging of APOBEC3G into Pr55 Gag virus-like particles and into HIV-1 virions is reduced when Nedd4-1 C/S is expressed. During HIV-1 viral production in the presence of APOBEC3G, Nedd4-1 C/S restores partially the infectivity of Δ
vif HIV-1. We conclude that the ubiquitination of APOBEC3G by Nedd4-1 favors its targeting to the virus assembly site where APOBEC3G interacts with Gag and is packaged into HIV-1 particles in the absence of Vif.
The genome of the jaagsiekte (JS) retrovirus (JSRV), the etiological agent of sheep pulmonary adenomatosis (jaagsiekte), has been identified, isolated, and partly cloned. The JSRV genome is ca. 8.7 ...kb long. EDNA of the genomic RNA was synthesized and cloned. A clone, JS 46.1, was isolated and characterized. It has an insert of 2.1 kb which hybridizes to the same 8.7-kb RNA in all the JSRV-infected sheep lung washes tested but does not hybridize to maedi-visna virus, a sheep lentivirus often found coinfecting JSRV-infected lungs. Comparison of the amino acid sequence encoded by JS 46.1 with those encoded by other retroviruses revealed that JSRV has homology to the type D and B oncoviruses and to human endogenous retrovirus
During the early step of the lytic cycle, visna provirus is first transcribed into two small multispliced mRNAs of 1.6 and 1.2 kilobases which may encode factors regulating the replication of visna ...virus (R. Vigne, V. Barban, G. Querat, V. Mazarin, T. Gourdou, and N. Sauze, Virology 161:218-217, 1987). By cDNA cloning and nucleotide sequencing, we determined that the 1.2-kilobase mRNA is 1,174 nucleotides long without the 3'-polyadenylated tail and is composed of four exons, two of which originated from the 5' and 3' ends,respectively, of the env gene region. Two overlapping open reading frames are present in each of these two exons. They were translated in vitro and gave riseto three proteins, two of 19 and 17 kilodaltons, termed VEP1, and one of 16.5 kilodaltons, termed STM. Only the VEP1 proteins were recognized by a hyperimmune anti-visna virus serum of infected sheep. Transient-expression assays performed in eucaryotic cells demonstrated that the cDNA clone describedhere has a trans-acting effect on transcription of the visna virus genes
Since the first report documenting that HIV-1 Vpr was involved in the stimulation of transactivation of several unrelated promoters, little additional information has been reported. By using ...transient transfection experiments, we confirmed and extended these previously reported data. Further
in vivoexperiments showed that Vpr can co-operatively stimulate transactivation activity of a minimal promoter containing one GAL4 DNA-binding site, when it is co-expressed with different heterologous activator domains fused to GAL4 DNA-binding domain. Thus, Vpr could transactivate in concert with an activator domain, but has no effect on the transactivation of a minimal promoter in the absence of activator protein. To investigate whether Vpr can interact with components of the basal transcriptional machinery,
in vitroprotein – protein binding assays were performed using either translated, radiolabeled Vpr or TFIIB proteins and glutathione
S-transferase Vpr or TFIIB chimeric proteins. We demon strated that the portion of Vpr ranging from amino acids 15 to 77 interacts specifically with the basal transcription factor TFIIB. Also, our data indicated that the N-terminal domain of TFIIB is required for the interaction.
Visna-maedi virus induces in sheep an interstitial lung disease characterised by an accumulation of smooth muscle cells (SMC) or myomatosis. Infection by HIV-1 has been recently associated with ...disorders of the vessel-derived cells: primary pulmonary hypertension, coronary artery disease and smooth muscle tumors in humans. We hypothesized that besides their regular targets (i.e. macrophages and lymphocytes), lentiviruses could infect smooth muscle cells. Smooth muscle cell cultures derived from ovine aorta were infected with visna-maedi virus strain K1514. The cultured cells were smooth muscle cells as demonstrated by their antigenic expression of alpha-actin and vimentin. The lentiviral infection of the smooth muscle cells was demonstrated by a typical cytopathic effect (syncytia), the expression of virus specific antigens and the presence of genomic RNA detected by Northern blot analysis and RT PCR. The detection of a reverse transcriptase activity, the presence of viral RNA in supernatants of infected smooth muscle cells detected by RT PCR and their ability to infect ovine permissive fibroblasts demonstrated a productive infection. The ability of smooth muscle cells to be infected by lentiviruses may participate in the pathogenesis of the tissue damage associated with the lentiviruses such as myomatosis in sheep and vascular disease in humans.
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