scholarly journals Isolation of Human Immunodeficiency Virus Type 1 Cores: Retention of Vpr in the Absence of p6gag

2000 ◽  
Vol 74 (13) ◽  
pp. 6198-6202 ◽  
Author(s):  
Molly A. Accola ◽  
Åsa Öhagen ◽  
Heinrich G. Göttlinger

ABSTRACT Mature human immunodeficiency virus type 1 (HIV-1) virions contain a typically cone-shaped core that encases the viral genome. In this study, we established conditions which allowed the efficient isolation of morphologically intact HIV-1 cores from virions. The isolated cores consisted mostly of cones which appeared uniformly capped at both ends but were heterogeneous with respect to the shape of the broad cap as well as the dimensions and angle of the cone. Vpr, a nonstructural virion component implicated in the nuclear import of the viral genome, was recovered in core preparations of HIV-1 and simian immunodeficiency viruses from African green monkeys. Unexpectedly, p6 gag , a structural protein required for the incorporation of Vpr, was absent from HIV-1 core preparations. Taken together, our results indicate that the incorporation of Vpr into the virion core is a conserved feature of primate lentiviruses and that the interactions required for the uptake of Vpr into assembling particles differ from those which confine Vpr within the core.

2008 ◽  
Vol 82 (21) ◽  
pp. 10864-10872 ◽  
Author(s):  
Angsana Phuphuakrat ◽  
Romchat Kraiwong ◽  
Chompunuch Boonarkart ◽  
Darat Lauhakirti ◽  
Tun-Hou Lee ◽  
...  

ABSTRACT ADARs (adenosine deaminases that act on double-stranded RNA) are RNA editing enzymes that catalyze a change from adenosine to inosine, which is then recognized as guanosine by translational machinery. We demonstrate here that overexpression of ADARs but not of an ADAR mutant lacking editing activity could upregulate human immunodeficiency virus type 1 (HIV-1) structural protein expression and viral production. Knockdown of ADAR1 by RNA silencing inhibited HIV-1 production. Viral RNA harvested from transfected ADAR1-knocked-down cells showed a decrease in the level of unspliced RNA transcripts. Overexpression of ADAR1 induced editing at a specific site in the env gene, and a mutant with the edited sequence was expressed more efficiently than the wild-type viral genome. These data suggested the role of ADAR in modulation of HIV-1 replication. Our data demonstrate a novel mechanism in which HIV-1 employs host RNA modification machinery for posttranscriptional regulation of viral protein expression.


1998 ◽  
Vol 72 (6) ◽  
pp. 4678-4685 ◽  
Author(s):  
Meenakshi Gaur ◽  
Andrew D. Leavitt

ABSTRACT The core domain of human immunodeficiency virus type 1 (HIV-1) integrase (IN) contains a D,D(35)E motif, named for the phylogenetically conserved glutamic acid and aspartic acid residues and the invariant 35 amino acid spacing between the second and third acidic residues. Each acidic residue of the D,D(35)E motif is independently essential for the 3′-processing and strand transfer activities of purified HIV-1 IN protein. Using a replication-defective viral genome with a hygromycin selectable marker, we recently reported that a mutation at any of the three residues of the D,D(35)E motif produces a 103- to 104-fold reduction in infectious titer compared with virus encoding wild-type IN (A. D. Leavitt et al., J. Virol. 70:721–728. 1996). The infectious titer, as measured by the number of hygromycin-resistant colonies formed following infection of cells in culture, was less than a few hundred colonies per μg of p24. To understand the mechanism by which the mutant virions conferred hygromycin resistance, we characterized the integrated viral DNA in cells infected with virus encoding mutations at each of the three residues of the D,D(35)E motif. We found the integrated viral DNA to be colinear with the incoming viral genome. DNA sequencing of the junctions between integrated viral DNA and host DNA showed that (i) the characteristic 5-bp direct repeat of host DNA flanking the HIV-1 provirus was not maintained, (ii) integration often produced a deletion of host DNA, (iii) integration sometimes occurred without the viral DNA first undergoing 3′-processing, (iv) integration sites showed a strong bias for a G residue immediately adjacent to the conserved viral CA dinucleotide, and (v) mutations at each of the residues of the D,D(35)E motif produced essentially identical phenotypes. We conclude that mutations at any of the three acidic residues of the conserved D,D(35)E motif so severely impair IN activity that most, if not all, integration events by virus encoding such mutations are not IN mediated. IN-independent provirus formation may have implications for anti-IN therapeutic agents that target the IN active site.


2000 ◽  
Vol 74 (24) ◽  
pp. 11811-11824 ◽  
Author(s):  
Kalpana Gupta ◽  
David Ott ◽  
Thomas J. Hope ◽  
Robert F. Siliciano ◽  
Jef D. Boeke

ABSTRACT Active nuclear import of the human immunodeficiency virus type 1 (HIV-1) preintegration complex (PIC) is essential for the productive infection of nondividing cells. Nuclear import of the PIC is mediated by the HIV-1 matrix protein, which also plays several critical roles during viral entry and possibly during virion production facilitating the export of Pr55Gag and genomic RNA. Using a yeast two-hybrid screen, we identified a novel human virion-associated matrix-interacting protein (VAN) that is highly conserved in vertebrates and expressed in most human tissues. Its expression is upregulated upon activation of CD4+ T cells. VAN is efficiently incorporated into HIV-1 virions and, like matrix, shuttles between the nucleus and cytoplasm. Furthermore, overexpression of VAN significantly inhibits HIV-1 replication in tissue culture. We propose that VAN regulates matrix nuclear localization and, by extension, both nuclear import of the PIC and export of Pr55Gag and viral genomic RNA during virion production. Our data suggest that this regulatory mechanism reflects a more global process for regulation of nucleocytoplasmic transport.


2002 ◽  
Vol 76 (23) ◽  
pp. 12087-12096 ◽  
Author(s):  
Jeffrey D. Dvorin ◽  
Peter Bell ◽  
Gerd G. Maul ◽  
Masahiro Yamashita ◽  
Michael Emerman ◽  
...  

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) can infect nondividing cells productively because the nuclear import of viral nucleic acids occurs in the absence of cell division. A number of viral factors that are present in HIV-1 preintegration complexes (PICs) have been assigned functions in nuclear import, including an essential valine at position 165 in integrase (IN-V165) and the central polypurine tract (cPPT). In this article, we report a comparison of the replication and infection characteristics of viruses with disruptions in the cPPT and IN-V165. We found that viruses with cPPT mutations still replicated productively in both dividing and nondividing cells, while viruses with a mutation at IN-V165 did not. Direct observation of the subcellular localization of HIV-1 cDNAs by fluorescence in situ hybridization revealed that cDNAs synthesized by both mutant viruses were readily detected in the nucleus. Thus, neither the cPPT nor the valine residue at position 165 of integrase is essential for the nuclear import of HIV-1 PICs.


2009 ◽  
Vol 84 (1) ◽  
pp. 397-406 ◽  
Author(s):  
Lavanya Krishnan ◽  
Kenneth A. Matreyek ◽  
Ilker Oztop ◽  
Kyeongeun Lee ◽  
Christopher H. Tipper ◽  
...  

ABSTRACT Recent genome-wide screens have highlighted an important role for transportin 3 in human immunodeficiency virus type 1 (HIV-1) infection and preintegration complex (PIC) nuclear import. Moreover, HIV-1 integrase interacted with recombinant transportin 3 protein under conditions whereby Moloney murine leukemia virus (MLV) integrase failed to do so, suggesting that integrase-transportin 3 interactions might underscore active retroviral PIC nuclear import. Here we correlate infectivity defects in transportin 3 knockdown cells with in vitro protein binding affinities for an expanded set of retroviruses that include simian immunodeficiency virus (SIV), bovine immunodeficiency virus (BIV), equine infectious anemia virus (EIAV), feline immunodeficiency virus (FIV), and Rous sarcoma virus (RSV) to critically address the role of integrase-transportin 3 interactions in viral infection. Lentiviruses, with the exception of FIV, display a requirement for transportin 3 in comparison to MLV and RSV, yielding an infection-based dependency ranking of SIV > HIV-1 > BIV and EIAV > MLV, RSV, and FIV. In vitro pulldown and surface plasmon resonance assays, in contrast, define a notably different integrase-transportin 3 binding hierarchy: FIV, HIV-1, and BIV > SIV and MLV > EIAV. Our results therefore fail to support a critical role for integrase binding in dictating transportin 3 dependency during retrovirus infection. In addition to integrase, capsid has been highlighted as a retroviral nuclear import determinant. Accordingly, MLV/HIV-1 chimera viruses pinpoint the genetic determinant of sensitization to transportin 3 knockdown to the HIV-1 capsid protein. We therefore conclude that capsid, not integrase, is the dominant viral factor that dictates transportin 3 dependency during HIV-1 infection.


2003 ◽  
Vol 77 (21) ◽  
pp. 11531-11535 ◽  
Author(s):  
Daniel Boden ◽  
Oliver Pusch ◽  
Frederick Lee ◽  
Lynne Tucker ◽  
Bharat Ramratnam

ABSTRACT Sequence-specific degradation of mRNA by short interfering RNA (siRNA) allows the selective inhibition of viral proteins that are critical for human immunodeficiency virus type 1 (HIV-1) replication. The aim of this study was to characterize the potency and durability of virus-specific RNA interference (RNAi) in cell lines that stably express short hairpin RNA (shRNA) targeting the HIV-1 transactivator protein gene tat. We found that the antiviral activity of tat shRNA was abolished due to the emergence of viral quasispecies harboring a point mutation in the shRNA target region. Our results suggest that, in order for RNAi to durably suppress HIV-1 replication, it may be necessary to target highly conserved regions of the viral genome. Alternatively, similar to present antiviral drug therapy paradigms, DNA constructs expressing multiple siRNAs need to be developed that target different regions of the viral genome, thereby reducing the probability of generating escape mutants.


2006 ◽  
Vol 80 (20) ◽  
pp. 10262-10269 ◽  
Author(s):  
Nathalie Arhel ◽  
Sandie Munier ◽  
Philippe Souque ◽  
Karine Mollier ◽  
Pierre Charneau

ABSTRACT We have previously established, using human immunodeficiency virus type 1 (HIV-1) strain LAI, that the HIV-1 central DNA Flap acts as a cis determinant of viral genome nuclear import. Although the impact of the DNA Flap on nuclear import has already found numerous independent confirmations in the context of lentivirus vectors, it has been claimed that it may be nonessential for infectious virus strains LAI, YU-2 (J. D. Dvorin et al., J. Virol. 76:12087-12096, 2002), HXB2, and NL4-3 (A. Limon et al., J. Virol. 76:12078-12086, 2002). We conducted a detailed analysis of virus infectivity using the provirus clones provided by the authors and analogous target cells. In contrast to published data, our results show that all cPPT mutant viruses exhibit reduced infectivity corresponding to a nuclear import defect irrespective of the viral genetic background or target cell.


2002 ◽  
Vol 76 (17) ◽  
pp. 8518-8531 ◽  
Author(s):  
Theodore C. Pierson ◽  
Yan Zhou ◽  
Tara L. Kieffer ◽  
Christian T. Ruff ◽  
Christopher Buck ◽  
...  

ABSTRACT Most current evidence suggests that the infection of resting CD4+ T cells by human immunodeficiency virus type 1 (HIV-1) is not productive due to partial or complete blocks in the viral life cycle at steps prior to integration of the viral genome into the host cell chromosome. However, stimulation of an infected resting T cell by antigen, cytokines, or microenvironmental factors can overcome these blocks and allow for the production of progeny virions. In this study, we sought to understand the structure and fate of the virus in unstimulated resting CD4+ T cells. Using a novel linker-mediated PCR assay designed to detect and characterize linear unintegrated forms of the HIV-1 genome, we demonstrate that reverse transcription can proceed to completion following the infection of resting T cells, generating the substrate for the retroviral integration reaction. However, reverse transcription in resting T cells is far slower than in activated T cells, requiring 2 to 3 days to complete. The delay in completing reverse transcription may make the viral DNA genome more susceptible to competing decay processes. To explore the relationship between the formation of the linear viral genome and the stability of the preintegration state, we employed a recombinant HIV-1 virus expressing the enhanced green fluorescent protein to measure the rate at which HIV-1 decays in the preintegration state. Our results demonstrate that the preintegration state is labile and decays rapidly (half-life = 1 day) following the entry of HIV-1 into a resting T cell, with significant decay occurring during the slow process of reverse transcription.


2003 ◽  
Vol 77 (13) ◽  
pp. 7582-7589 ◽  
Author(s):  
Michael P. Sherman ◽  
Carlos M. C. de Noronha ◽  
Lauren A. Eckstein ◽  
Jason Hataye ◽  
Pamela Mundt ◽  
...  

ABSTRACT Retroviruses must gain access to the host cell nucleus for subsequent replication and viral propagation. Human immunodeficiency virus type 1 (HIV-1) and other primate lentiviruses are distinguished from the gammaretroviruses by their ability to infect nondividing cells such as macrophages, an important viral reservoir in vivo. Rather than requiring nuclear membrane breakdown during cell division, the HIV-1 preintegration complex (PIC) enters the nucleus by traversing the central aqueous channel of the limiting nuclear pore complex. The HIV-1 PIC contains three nucleophilic proteins, matrix, integrase, and Vpr, all of which have been implicated in nuclear targeting. The mechanism by which Vpr can display such nucleophilic properties and yet also be available for incorporation into virions assembling at the plasma membrane is unresolved. We recently characterized Vpr as a nucleocytoplasmic shuttling protein that contains two novel nuclear import signals and an exportin-1-dependent nuclear export signal (NES). We now demonstrate that mutation of this NES impairs the incorporation of Vpr into newly formed virions. Furthermore, we find that the Vpr NES is required for efficient HIV replication in tissue macrophages present in human spleens and tonsils. These findings underscore how the nucleocytoplasmic shuttling of Vpr not only contributes to nuclear import of the HIV-1 PIC but also enables Vpr to be present in the cytoplasm for incorporation into virions, leading to enhancement of viral spread within nondividing tissue macrophages.


2004 ◽  
Vol 78 (21) ◽  
pp. 11563-11573 ◽  
Author(s):  
Tamako Ikeda ◽  
Hironori Nishitsuji ◽  
Xin Zhou ◽  
Nobuo Nara ◽  
Takashi Ohashi ◽  
...  

ABSTRACT Nuclear import of viral cDNA is a critical step for establishing the proviral state of human immunodeficiency virus type 1 (HIV-1). The contribution of HIV-1 integrase (IN) to the nuclear import of viral cDNA is controversial, partly due to a lack of identification of its bona fide nuclear localization signal. In this study, to address this putative function of HIV-1 IN, the effects of mutations at key residues for viral cDNA recognition (PYNP at positions 142 to 145, K156, K159, and K160) were evaluated in the context of viral replication. During acute infection, some mutations (N144Q, PYNP>KL, and KKK>AAA) severely reduced viral gene expression to less than 1% the wild-type (WT) level. None of the mutations affected the synthesis of viral cDNA. Meanwhile, the levels of integrated viral cDNA produced by N144Q, PYNP>KL, and KKK>AAA mutants were severely reduced to less than 1% the WT level. Quantitative PCR analysis of viral cDNA in nuclei and fluorescence in situ hybridization analysis showed that these mutations significantly reduced the level of viral cDNA accumulation in nuclei. Further analysis revealed that IN proteins carrying the N144Q, PYNP>KL, and KKK>AAA mutations showed severely reduced binding to viral cDNA but kept their karyophilic properties. Taken together, these results indicate that mutations that reduced the binding of IN to viral cDNA resulted in severe impairment of virus infectivity, most likely by affecting the nuclear import of viral cDNA that proceeds integration. These results suggest that HIV-1 IN may be one of the critical constituents for the efficient nuclear import of viral cDNA.


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