Infection by lentiviruses such as human immunodeficiency virus, Maedi-Visna virus and Caprine Arthritis Encephalitis Virus, is associated with a variety of neurological syndromes, but the mechanism ...by which the damage occurs to the nervous system is not known. The viruses do not infect neurons and so the neurotoxic actions must be mediated indirectly. Here we applied synthetic peptide analogues derived from basic regions of Maedi-Visna virus and human immunodeficiency virus transactivating protein, tat, to rat brain in vivo and found them to be potent neurotoxins. The toxicity of the Maedi-Visna virus peptide was demonstrated to be reduced by blockade of nitric oxide synthase and of N-methyl-D-aspartate channel opening. These experiments suggest that peptides derived from lentiviral tat may share a common neurotoxic action.
In 1962 a group of liberals in Cape Town founded The New African as a radical review of politics and the arts. It set out to cover the new Africa in general and South Africa in particular. At that ...time many countries in Africa were gaining their independence and this group intended that a non-racial democratic South Africa would join them sooner rather than later. The editors set out to learn from, to criticise and rejoice in the changes which were happening in the far away north of the African continent. Thanks especially to Zeke Mphahlele the journal was always introducing to South Africa work by new writers such as Soyinka, Ngugi, Bessie Head, Dennis Brutus, Ayi Kwei Armah and Mazisi Kunene. In 1964 Special Branch harassment increased: the office was closed, the addressograph plates removed, all copies of the March issue seized at the Post Office, printers threatened, and a charge of obscenity and blasphemy brought for certain words like "Jeeweesus" in a shebeen story by Can Themba. The last South African issue was in July 1964, as three editors escaped in dangerously dramatic ways. The New African continued in London from March 1965 and free copies were sent to old subscribers in South Africa under a succession of fake mastheads to slip past the postal authorities.
The viral infectivity factor (Vif) protein of human immunodeficiency virus type 1 (HIV-1) is essential for viral replication
in vivo. Packaging of Vif into viral particles is mediated by an ...interaction with viral genomic RNA and association with viral nucleoprotein complexes. Despite recent findings on the RNA-binding properties of Vif suggesting that Vif could be involved in retroviral assembly, no RNA sequence or structure specificity has been determined so far. To gain further insight into the mechanisms by which Vif might regulate viral replication, we studied the interactions of Vif with HIV-1 genomic RNA
in vitro. Using extensive biochemical analysis, we have measured the affinity of recombinant Vif proteins for synthetic RNAs corresponding to various regions of the HIV-1 genome. We found that recombinant Vif proteins bind specifically to HIV-1 viral RNA fragments corresponding to the 5′-untranslated region (5′-UTR),
gag and the 5′ part of
pol (
K
d between 45
nM and 65
nM). RNA encompassing nucleotides 1–497 or 499–996 of the HIV-1 genomic RNA bind 9±2 and 21±3 Vif molecules, respectively, and at least some of these proteins bind in a cooperative manner (Hill constant α
H=2.3). In contrast, RNAs corresponding to other parts of the HIV-1 genome or heterologous RNAs showed poor binding capacity and weak cooperativity (
K
d>200
nM). Moreover, RNase T
1 footprinting revealed a hierarchical binding of Vif, pointing to TAR and the poly(A) stem-loop structures as primary strong affinity targets, and downstream structures as secondary sites with moderate affinity. Taken together, our findings suggest that Vif may assist other proteins to maintain a correct folding of the genomic RNA in order to facilitate its packaging and further steps such as reverse transcription. Interestingly, our results suggest also that Vif could bind the viral RNA in order to protect it from the action of the antiviral factor APOBEC-3G/3F.
We used multiple regression and hierarchical mixed‐effects models to examine spatial patterns of overwinter survival and size at smolting in juvenile coho salmon Oncorhynchus kisutch in relation to ...habitat attributes across an extensive stream network in southwestern Oregon over 3 years. Contributing basin area explained the majority of spatial variation (R2 = 0.57‐0.63) in coho salmon overwinter survival (range = 0.02‐0.63), with highest survival rates observed in smaller headwater and intermittent streams. Other habitat attributes, including proportional pool area, percent exposed bedrock substrate, percent broadleaf canopy cover, and adult salmon carcass density, were relatively poor predictors of survival. Indices of individual fish condition, including fall parr fork length, condition factor, and parasite infestation rates, were also relatively uninformative in coho salmon overwinter survival models. Coho salmon smolt length was primarily a function of length at the time of fall tagging, but stream type, contributing basin area (positive effect), thermal history (positive effect), and black spot infestation (i.e., trematode metacercariae; negative effect) were also important. The consistent, broad spatial gradients in overwinter survival observed in this study can help guide efforts designed to enhance coho salmon production in coastal streams and suggest that habitat protection, restoration, and enhancement strategies will be best guided by a whole‐basin context.
Caprine arthritis encephalitis virus (CAEV) is a lentivirus closely related to visna virus and more distantly to other lentiviruses, such as human immunodeficiency virus. The genomes of visna virus ...and CAEV contain a tat gene encoding a protein able to weakly transactivate its own long terminal repeat, suggesting that transactivation may be a dispensable function for viral replication. Three different tat gene mutants of an infectious molecular clone of CAEV were used to study their replication after transfection or infection of primary goat synovial membrane cells and of blood-derived mononuclear cells or macrophages. Our results showed no difference between replication of the wild type and either the complete tat deletion mutant or the tat stop point mutant, whereas slower growth kinetics and lower levels of expression of the partial tat deletion mutant than of the wild type were obtained in these cells. Quantitative PCR and reverse transcription-PCR analyses of the different steps of a single replicative cycle revealed an identical pattern of retrotranscription, transcription, and viral production, whereas time course analysis demonstrated that the intracellular level of viral genomic RNA was affected by the partial tat deletion at later time points. We then compared the infectious properties of the wild-type and tat mutant viruses in vivo by direct inoculation of proviral DNAs into the joints of goats. All the animals seroconverted between 27 and 70 days postinoculation. Moreover, we were able to isolate tat mutant CAEV from blood-derived macrophages that was still able to infect synovial membrane cells in vitro. This study clearly demonstrates that the tat gene of CAEV is dispensable for viral replication in vitro and in vivo
Complex retrovirus genomes contain a variable number of accessory genes, among which is the vif gene. We investigated in vitro the role of the vif gene of caprine arthritis encephalitis virus (CAEV) ...by studying the phenotype live vif mutants after infection of primary goat synovial membrane (GSM) cells and blood-derived monocytes/macrophages. Any deletion introduced into the vif gene resulted In slow and low viral replication and production of virions with an infectious titer lower than that of wild-type viral particles. The wild-type phenotype could be restored by the trans expression of the vif gene in a complementation assay. Quantitative PCR and reverse transcription PCR analyses were performed in order to determine which stage of the replicative cycle was impaired by the vif deletion. Our results demonstrated that CAEV Vif did not act at the level of reverse transcription or transcription but rather at the late stage of virus formation and/or release, as lower amounts of virus were produced after a single replicative cycle. The vif deleted CAEV produced after 24 h of infection was still able to infect GSM cells indicating that the vif gene is not essential for virus infectivity but is required for efficient virus production
The viral infectivity factor (Vif), one of the six HIV-1 auxiliary genes, is absolutely necessary for productive infection in primary CD4-positive T lymphocytes and macrophages. Vif overcomes the ...antiviral function of the host factor APOBEC3G. To better understand this mechanism, it is of interest to characterize cellular proteins that interact with Vif and may regulate its function. Here, we show that Vif binds to hNedd4 and AIP4, two HECT E3 ubiquitin ligases. WW domains present in those HECT enzymes contribute to the binding of Vif. Moreover, the region of Vif, which includes amino acids 20–128 and interacts with the hNedd4 WW domains, does not contain proline-rich stretches. Lastly, we show that Vif undergoes post-translational modifications by addition of ubiquitin both in cells overexpressing Vif and in cells expressing HIV-1 provirus. Vif is mainly mono-ubiquitinated, a modification known to address the Gag precursor to the virus budding site.
The virus infectivity factor (Vif) protein facilitates the replication of human immunodeficiency virus type 1 (HIV-1) in primary lymphocytes and macrophages. Its action is strongly dependent on the ...cellular environment, and it has been proposed that the Vif protein counteracts cellular activities that would otherwise limit HIV-1 replication. Using a glutathione S-transferase pull-down assay, we identified that Vif binds specifically to the Src homology 3 domain of Hck, a tyrosine kinase from the Src family. The interaction between Vif and the full-length Hck was further assessed by co-precipitation assays in vitro and in human cells. The Vif protein repressed the kinase activity of Hck and was not itself a substrate for Hck phosphorylation. Within one single replication cycle of HIV-1, Hck was able to inhibit the production and the infectivity ofvif-deleted virus but not that of wild-type virus. Accordingly, HIV-1 vif−replication was delayed in Jurkat T cell clones stably expressing Hck. Our data demonstrate that Hck controls negatively HIV-1 replication and that this inhibition is suppressed by the expression of Vif. Hck, which is present in monocyte-macrophage cells, represents the first identified cellular inhibitor of HIV-1 replication overcome by Vif.
The main function of Vif is to limit the antiviral activity of APOBEC3G by counteracting its packaging into HIV-1 virions. In this work, we examine the possible functional interactions between Vif, ...APOBEC3G, and two Src family tyrosine kinases, Fyn and Hck, present in T lymphocytes and in monocyte–macrophages, respectively. By GST pull-down, we show that the SH3 domains of Fyn and Hck, and the corresponding full-length proteins bind Vif of HIV-1. One consequence of this interaction is a reduction in their catalytic activity. Interestingly, we also observed that APOBEC3G can be phosphorylated on tyrosine in the presence of Fyn or Hck, suggesting that both kinases may regulate APOBEC3G function. Accordingly, we demonstrate that in the presence of Fyn or Hck and in the absence of Vif, the overall level of APOBEC3G incorporated into HIV-1 particles is decreased, whereas the level of encapsidation of its phosphorylated form is significantly enhanced.
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