Lentiviral RNAs can use different mechanisms for translation initiation

2008 ◽  
Vol 36 (4) ◽  
pp. 690-693 ◽  
Author(s):  
Emiliano P. Ricci ◽  
Ricardo Soto Rifo ◽  
Cécile H. Herbreteau ◽  
Didier Decimo ◽  
Théophile Ohlmann
Keyword(s):  
Genomic Rna ◽  
Coding Region ◽  
Entry Site ◽  
Rna Motifs ◽  
Internal Ribosome Entry ◽  
Gag Polyprotein ◽  
Immunodeficiency Virus ◽  
Reticulocyte Lysate ◽  
Hiv 1 ◽  
Dependent Mechanism

The full-length genomic RNA of lentiviruses can be translated to produce proteins and incorporated as genomic RNA in the viral particle. Interestingly, both functions are driven by the genomic 5′-UTR (5′-untranslated region), which harbours structural RNA motifs for the replication cycle of the virus. Recent work has shown that this RNA architecture also functions as an IRES (internal ribosome entry site) in HIV-1 and -2, and in SIV (simian immunodeficiency virus). In addition, the IRES extends to the gag coding region for all these viruses and this leads to the synthesis of shorter isoforms of the Gag polyprotein from downstream initiation codons. In the present study, we have investigated how different members of the lentivirus family (namely HIV-1 and -2, and SIV) can initiate protein synthesis by distinct mechanisms. For this, we have used the competitive reticulocyte lysate that we have recently described. Our results show that HIV-1 is able to drive the synthesis of the Gag polyprotein both by a classical cap-dependent mechanism and an IRES, whereas HIV-2 and SIV appear to use exclusively an IRES mechanism.

scholarly journals A Dormant Internal Ribosome Entry Site Controls Translation of Feline Immunodeficiency Virus

2008 ◽  
Vol 82 (7) ◽  
pp. 3574-3583 ◽  
Author(s):  
Valentina Camerini ◽  
Didier Decimo ◽  
Laurent Balvay ◽  
Mauro Pistello ◽  
Mauro Bendinelli ◽  
...  
Keyword(s):  
Feline Immunodeficiency Virus ◽  
In Vitro Translation ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Immunodeficiency Virus ◽  
Specific Stimulation ◽  
Dependent Mechanism

ABSTRACT The characterization of internal ribosome entry sites (IRESs) in virtually all lentiviruses prompted us to investigate the mechanism used by the feline immunodeficiency virus (FIV) to produce viral proteins. Various in vitro translation assays with mono- and bicistronic constructs revealed that translation of the FIV genomic RNA occurred both by a cap-dependent mechanism and by weak internal entry of the ribosomes. This weak IRES activity was confirmed in feline cells expressing bicistronic RNAs containing the FIV 5′ untranslated region (UTR). Surprisingly, infection of feline cells with FIV, but not human immunodeficiency virus type 1, resulted in a great increase in FIV translation. Moreover, a change in the cellular physiological condition provoked by heat stress resulted in the specific stimulation of expression driven by the FIV 5′ UTR while cap-dependent initiation was severely repressed. These results reveal the presence of a “dormant” IRES that becomes activated by viral infection and cellular stress.

scholarly journals The Human Immunodeficiency Virus Type 1gag Gene Encodes an Internal Ribosome Entry Site

2001 ◽  
Vol 75 (1) ◽  
pp. 181-191 ◽  
Author(s):  
Christopher B. Buck ◽  
Xuefei Shen ◽  
Michael A. Egan ◽  
Theodore C. Pierson ◽  
Christopher M. Walker ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Internal Ribosome Entry Site ◽  
Cultured Cells ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Translational Initiation ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Several retroviruses have recently been shown to promote translation of their gag gene products by internal ribosome entry. In this report, we show that mRNAs containing the human immunodeficiency virus type 1 (HIV-1) gag open reading frame (ORF) exhibit internal ribosome entry site (IRES) activity that can promote translational initiation of Pr55 gag . Remarkably, this IRES activity is driven by sequences within the gag ORF itself and is not dependent on the native gag 5′-untranslated region (UTR). This cap-independent mechanism for Pr55 gag translation may help explain the high levels of translation of this protein in the face of major RNA structural barriers to scanning ribosomes found in the gag 5′ UTR. The gag IRES activity described here also drives translation of a novel 40-kDa Gag isoform through translational initiation at an internal AUG codon found near the amino terminus of the Pr55 gag capsid domain. Our findings suggest that this low-abundance Gag isoform may be important for wild-type replication of HIV-1 in cultured cells. The activities of the HIV-1 gag IRES may be an important feature of the HIV-1 life cycle and could serve as a novel target for antiretroviral therapeutic strategies.

scholarly journals The Leader of Human Immunodeficiency Virus Type 1 Genomic RNA Harbors an Internal Ribosome Entry Segment That Is Active during the G2/M Phase of the Cell Cycle

2003 ◽  
Vol 77 (7) ◽  
pp. 3939-3949 ◽  
Author(s):  
Ann Brasey ◽  
Marcelo Lopez-Lastra ◽  
Theophile Ohlmann ◽  
Nancy Beerens ◽  
Ben Berkhout ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Protein Synthesis ◽  
Human Immunodeficiency Virus Type ◽  
Genomic Rna ◽  
M Cell ◽  
Internal Ribosome Entry ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The 5′ leader of the human immunodeficiency virus type 1 (HIV-1) genomic RNA contains highly structured domains involved in key steps of the viral life cycle. These RNA domains inhibit cap-dependent protein synthesis. Here we report that the HIV-1 5′ leader harbors an internal ribosome entry site (IRES) capable of driving protein synthesis during the G2/M cell cycle phase in which cap-dependent initiation is inhibited. The HIV-1 IRES was delineated with bicistronic mRNAs in in vitro and ex vivo assays. The HIV-1 leader IRES spans nucleotides 104 to 336 and partially overlaps the major determinants of genomic RNA packaging. These data strongly suggest that, as for HIV-1 transcription, IRES-mediated translation initiation could play an important role in virus replication during virus-induced G2/M cell cycle arrest.

scholarly journals Structure, Function, and Interactions of the HIV-1 Capsid Protein

Life ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 100
Author(s):  
Eric Rossi ◽  
Megan E. Meuser ◽  
Camille J. Cunanan ◽  
Simon Cocklin
Keyword(s):  
Life Cycle ◽  
Capsid Protein ◽  
Adaptor Proteins ◽  
Restriction Factors ◽  
Gag Polyprotein ◽  
Immunodeficiency Virus ◽  
Host Cell Factors ◽  
Hiv 1

The capsid (CA) protein of the human immunodeficiency virus type 1 (HIV-1) is an essential structural component of a virion and facilitates many crucial life cycle steps through interactions with host cell factors. Capsid shields the reverse transcription complex from restriction factors while it enables trafficking to the nucleus by hijacking various adaptor proteins, such as FEZ1 and BICD2. In addition, the capsid facilitates the import and localization of the viral complex in the nucleus through interaction with NUP153, NUP358, TNPO3, and CPSF-6. In the later stages of the HIV-1 life cycle, CA plays an essential role in the maturation step as a constituent of the Gag polyprotein. In the final phase of maturation, Gag is cleaved, and CA is released, allowing for the assembly of CA into a fullerene cone, known as the capsid core. The fullerene cone consists of ~250 CA hexamers and 12 CA pentamers and encloses the viral genome and other essential viral proteins for the next round of infection. As research continues to elucidate the role of CA in the HIV-1 life cycle and the importance of the capsid protein becomes more apparent, CA displays potential as a therapeutic target for the development of HIV-1 inhibitors.

scholarly journals Human Immunodeficiency Virus Type 1 Nucleocapsid Protein Nuclear Localization Mediates Early Viral mRNA Expression

2002 ◽  
Vol 76 (20) ◽  
pp. 10444-10454 ◽  
Author(s):  
Jielin Zhang ◽  
Clyde S. Crumpacker
Keyword(s):  
Human Immunodeficiency Virus ◽  
Mrna Expression ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nucleocapsid Protein ◽  
Viral Mrna ◽  
Genomic Rna ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT An important aspect of the pathophysiology of human immunodeficiency virus type 1 (HIV-1) infection is the ability of the virus to replicate in the host vigorously without a latent phase and to kill cells with a dynamic turnover of 1.8 × 109 cells/day and 10.3 × 109 virions/24 h. The transcription of HIV-1 RNA in acute infection occurs at two stages; the transcription of viral spliced mRNA occurs early, and the transcription of viral genomic RNA occurs later. The HIV-1 Tat protein is translated from the early spliced mRNA and is critical for HIV-1 genomic RNA expression. The cellular transcription factors are important for HIV-1 early spliced mRNA expression. In this study we show that virion nucleocapsid protein (NC) has a role in expression of HIV-1 early spliced mRNA. The HIV-1 NC migrates from the cytoplasm to the nucleus and accumulates in the nucleus at 18 h postinfection. Mutations on HIV-1 NC zinc fingers change the pattern of early viral spliced mRNA expression and result in a delayed expression of early viral mRNA in HIV-infected cells. This delayed HIV-1 early spliced mRNA expression occurs after proviral DNA has been integrated into the cellular genome, as shown by a quantitative integration assay. These results show that virion NC plays an important role in inducing HIV-1 early mRNA expression and contributes to the rapid viral replication that occurs during HIV-1 infection.

scholarly journals Immature HIV-1 Lattice Assembly Dynamics are Regulated by Scaffolding from Nucleic Acid and the Plasma Membrane

2017 ◽  
Author(s):  
Alexander J. Pak ◽  
John M. A. Grime ◽  
Prabuddha Sengupta ◽  
Antony K. Chen ◽  
Aleksander E. P. Durumeric ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Nucleic Acid ◽  
Structural Data ◽  
Single Particle Tracking ◽  
Coarse Grained ◽  
Intermediate Step ◽  
Amino Terminal ◽  
Gag Polyprotein ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACTThe packaging and budding of Gag polyprotein and viral ribonucleic acid (RNA) is a critical step in the human immunodeficiency virus-1 (HIV-1) lifecycle. High-resolution structures of the Gag polyprotein have revealed that the capsid (CA) and spacer peptide 1 (SP1) domains contain important interfaces for Gag self-assembly. However, the molecular details of the multimerization process, especially in the presence of RNA and the cell membrane, have remained unclear. In this work, we investigate the mechanisms that work in concert between the polyproteins, RNA, and membrane to promote immature lattice growth. We develop a coarse-grained (CG) computational model that is derived from sub-nanometer resolution structural data. Our simulations recapitulate contiguous and hexameric lattice assembly driven only by weak anisotropic attractions at the helical CA-SP1 junction. Importantly, analysis from CG and single-particle tracking photoactivated localization (spt-PALM) trajectories indicates that viral RNA and the membrane are critical constituents that actively promote Gag multimerization through scaffolding, while over-expression of short competitor RNA can suppress assembly. We also find that the CA amino-terminal domain imparts intrinsic curvature to the Gag lattice. As a consequence, immature lattice growth appears to be coupled to the dynamics of spontaneous membrane deformation. Our findings elucidate a simple network of interactions that regulate the early stages of HIV-1 assembly and budding.SIGNIFICANCE STATEMENTIn order for human immunodeficiency virus to proliferate, viral proteins and genomic dimers are assembled at host cell membranes and released as immature virions. Disrupting this key intermediate step in viral replication is a potential target for treatment. However, a detailed molecular view of this process remains lacking. Here, we elucidate a network of constitutive interactions that regulate viral assembly dynamics through a combined computational and experimental approach. Specifically, our analysis reveals the active roles of nucleic acid and the membrane as scaffolds that promote the multimerization of Gag polyprotein which proceeds through multi-step and self-correcting nucleation. Our findings also illustrate the functional importance of the N-terminal, C-terminal, and spacer peptide 1 protein domains.

scholarly journals A Human Nuclear Shuttling Protein That Interacts with Human Immunodeficiency Virus Type 1 Matrix Is Packaged into Virions

2000 ◽  
Vol 74 (24) ◽  
pp. 11811-11824 ◽  
Author(s):  
Kalpana Gupta ◽  
David Ott ◽  
Thomas J. Hope ◽  
Robert F. Siliciano ◽  
Jef D. Boeke
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Import ◽  
Productive Infection ◽  
Genomic Rna ◽  
Virion Production ◽  
Immunodeficiency Virus ◽  
Hiv 1

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.

Does HIV-1 mRNA 5'-untranslated region bear an internal ribosome entry site?

Biochimie ◽  
2016 ◽  
Vol 121 ◽  
pp. 228-237 ◽  
Author(s):  
Victoria V. Smirnova ◽  
Ilya M. Terenin ◽  
Anastasia A. Khutornenko ◽  
Dmitri E. Andreev ◽  
Sergey E. Dmitriev ◽  
...  
Keyword(s):  
Internal Ribosome Entry Site ◽  
Untranslated Region ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Hiv 1

scholarly journals The Human Immunodeficiency Virus Type 1 Tat Protein Enhances Cryptosporidium parvum-Induced Apoptosis in Cholangiocytes via a Fas Ligand-Dependent Mechanism

2006 ◽  
Vol 75 (2) ◽  
pp. 684-696 ◽  
Author(s):  
Steven P. O'Hara ◽  
Aaron J. Small ◽  
Jeremy B. Nelson ◽  
Andrew D. Badley ◽  
Xian-Ming Chen ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Cryptosporidium Parvum ◽  
Fas Ligand ◽  
Tat Protein ◽  
Immunodeficiency Virus ◽  
Induced Apoptosis ◽  
Hiv 1 ◽  
Dependent Mechanism

ABSTRACT While Cryptosporidium parvum infection of the intestine has been reported in both immunocompetent and immunocompromised individuals, biliary infection is seen primarily in adult AIDS patients and is associated with development of AIDS cholangiopathy. However, the mechanisms of pathogen-induced AIDS cholangiopathy remain unclear. Since we previously demonstrated that the Fas/Fas ligand (FasL) system is involved in paracrine-mediated C. parvum cytopathicity in cholangiocytes, we also tested the potential synergistic effects of human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat)-mediated FasL regulation on C. parvum-induced apoptosis in cholangiocytes by semiquantitative reverse transcription-PCR, immunoblotting, immunofluorescence analysis, and immunogold electron microscopy. H69 cells do not express CXCR4 and CCR5, which are receptors required for direct HIV-1 viral infection. However, recombinant biologically active HIV-1-associated Tat protein increased FasL expression in the cytoplasm of cholangiocytes without a significant increase in apoptosis. We found that C. parvum-induced apoptosis was associated with translocation of intracellular FasL to the cell membrane surface and release of full-length FasL from infected H69 cells. Tat significantly (P < 0.05) increased C. parvum-induced apoptosis in bystander cells in a dose-dependent manner. Moreover, Tat enhanced both C. parvum-induced FasL membrane translocation and release of full-length FasL. In addition, the FasL neutralizing antibody NOK-1 and the caspase-8 inhibitor Z-IETD-fmk both blocked C. parvum-induced apoptosis in cholangiocytes. The data demonstrated that HIV-1 Tat enhances C. parvum-induced cholangiocyte apoptosis via a paracrine-mediated, FasL-dependent mechanism. Our results suggest that concurrent active HIV replication, with associated production of Tat protein, and C. parvum infection synergistically increase cholangiocyte apoptosis and thus jointly contribute to AIDS-related cholangiopathies.

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