scholarly journals Human Immunodeficiency Virus Type 1 Vpr Induces Apoptosis through Caspase Activation

2000 ◽  
Vol 74 (7) ◽  
pp. 3105-3111 ◽  
Author(s):  
Sheila A. Stewart ◽  
Betty Poon ◽  
Joo Y. Song ◽  
Irvin S. Y. Chen
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Ectopic Expression ◽  
Caspase Activity ◽  
Immunodeficiency Virus ◽  
Induced Apoptosis ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Vpr is a 96-amino-acid protein that is found associated with the HIV-1 virion. Vpr induces cell cycle arrest at the G2/M phase of the cell cycle, and this arrest is followed by apoptosis. We examined the mechanism of Vpr-induced apoptosis and found that HIV-1 Vpr-induced apoptosis requires the activation of a number of cellular cysteinyl aspartate-specific proteases (caspases). We demonstrate that ectopic expression of anti-apoptotic viral proteins, which inhibit caspase activity, and addition of synthetic peptides, which represent caspase cleavage sites, can inhibit Vpr-induced apoptosis. Finally, inhibition of caspase activity and subsequent inhibition of apoptosis results in increased viral expression, suggesting that therapeutic strategies aimed at reducing Vpr-induced apoptosis in vivo require careful consideration.

scholarly journals Human Immunodeficiency Virus Type 1 (HIV-1) Vpr Enhances Expression from Unintegrated HIV-1 DNA

2003 ◽  
Vol 77 (7) ◽  
pp. 3962-3972 ◽  
Author(s):  
Betty Poon ◽  
Irvin S. Y. Chen
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Cell Cycle Arrest ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Viral Dna ◽  
Cycle Arrest ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Retroviral DNA synthesized prior to integration, termed unintegrated viral DNA, is classically believed to be transcriptionally inert and to serve only as a precursor to the transcriptionally active integrated proviral DNA form. However, it has recently been found to be expressed under some circumstances during human immunodeficiency virus type 1 (HIV-1) replication and may play a significant role in HIV-1 pathogenesis. HIV-1 Vpr is a virion-associated accessory protein that is critical for HIV-1 replication in nondividing cells and induces cell cycle arrest and apoptosis. We find that Vpr, either expressed de novo or released from virions following viral entry, is essential for unintegrated viral DNA expression. HIV-1 mutants defective for integration in either the integrase catalytic domain or the cis-acting att sites can express unintegrated viral DNA at levels similar to that of wild-type HIV-1, but only in the presence of Vpr. In the absence of Vpr, the expression of unintegrated viral DNA decreases 10- to 20-fold. Vpr does not affect the efficiency of integration from integrase-defective HIV-1. Vpr-mediated enhancement of expression from integrase-defective HIV-1 requires that the viral DNA be generated in cells through infection and is mediated via a template that declines over time. Vpr activation of expression does not require exclusive nuclear localization of Vpr nor does it correlate with Vpr-mediated cell cycle arrest. These results attribute a new function to HIV-1 Vpr and implicate Vpr as a critical component in expression from unintegrated HIV-1 DNA.

scholarly journals Human Immunodeficiency Virus Type 1 Vpr-Binding Protein VprBP, a WD40 Protein Associated with the DDB1-CUL4 E3 Ubiquitin Ligase, Is Essential for DNA Replication and Embryonic Development

2008 ◽  
Vol 28 (18) ◽  
pp. 5621-5633 ◽  
Author(s):  
Chad M. McCall ◽  
Paula L. Miliani de Marval ◽  
Paul D. Chastain ◽  
Sarah C. Jackson ◽  
Yizhou J. He ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Dna Replication ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Binding Protein ◽  
S Phase ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Damaged DNA binding protein 1, DDB1, bridges an estimated 90 or more WD40 repeats (DDB1-binding WD40, or DWD proteins) to the CUL4-ROC1 catalytic core to constitute a potentially large number of E3 ligase complexes. Among these DWD proteins is the human immunodeficiency virus type 1 (HIV-1) Vpr-binding protein VprBP, whose cellular function has yet to be characterized but has recently been found to mediate Vpr-induced G2 cell cycle arrest. We demonstrate here that VprBP binds stoichiometrically with DDB1 through its WD40 domain and through DDB1 to CUL4A, subunits of the COP9/signalsome, and DDA1. The steady-state level of VprBP remains constant during interphase and decreases during mitosis. VprBP binds to chromatin in a DDB1-independent and cell cycle-dependent manner, increasing from early S through G2 before decreasing to undetectable levels in mitotic and G1 cells. Silencing VprBP reduced the rate of DNA replication, blocked cells from progressing through the S phase, and inhibited proliferation. VprBP ablation in mice results in early embryonic lethality. Conditional deletion of the VprBP gene in mouse embryonic fibroblasts results in severely defective progression through S phase and subsequent apoptosis. Our studies identify a previously unknown function of VprBP in S-phase progression and suggest the possibility that HIV-1 Vpr may divert an ongoing chromosomal replication activity to facilitate viral replication.

scholarly journals Human Immunodeficiency Virus Type 1 Vif Induces Cell Cycle Delay via Recruitment of the Same E3 Ubiquitin Ligase Complex That Targets APOBEC3 Proteins for Degradation

2008 ◽  
Vol 82 (18) ◽  
pp. 9265-9272 ◽  
Author(s):  
Jason L. DeHart ◽  
Alberto Bosque ◽  
Reuben S. Harris ◽  
Vicente Planelles
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Ubiquitin Ligase ◽  
Cell Cycle Delay ◽  
Immunodeficiency Virus ◽  
Apobec3 Proteins ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Vif recruits a Cullin 5 ubiquitin ligase that targets APOBEC3 proteins for degradation. Recently, Vif has also been shown to induce cell cycle disturbance in G2. We show that in contrast to the expression of Vpr, the expression of Vif does not preclude cell division, and therefore, Vif causes delay and not arrest in G2. We also demonstrate that the interaction of Vif with the ubiquitin ligase is required for cell cycle disruption, as was previously shown for HIV-1 Vpr. The presence of APOBEC3 D/E, F, and G had no influence on Vif-induced alteration of the cell cycle. We conclude that cell cycle delay by Vif is a result of ubiquitination and degradation of a cellular protein that is different from the known APOBEC3 family members.

scholarly journals Fusion-Induced Apoptosis Contributes to Thymocyte Depletion by a Pathogenic Human Immunodeficiency Virus Type 1 Envelope in the Human Thymus

2006 ◽  
Vol 80 (22) ◽  
pp. 11019-11030 ◽  
Author(s):  
Eric G. Meissner ◽  
Liguo Zhang ◽  
S. Jiang ◽  
Lishan Su
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Caspase 3 ◽  
Fusion Inhibitors ◽  
Immunodeficiency Virus ◽  
Induced Apoptosis ◽  
Hiv 1 ◽  
Active Caspase

ABSTRACT The mechanisms of CD4+ T-cell depletion during human immunodeficiency virus type 1 (HIV-1) infection remain incompletely characterized. Of particular importance is how CD4+ T cells are depleted within the lymphoid organs, including the lymph nodes and thymus. Herein we characterize the pathogenic mechanisms of an envelope from a rapid progressor (R3A Env) in the NL4-3 backbone (NL4-R3A) which is able to efficiently replicate and deplete CD4+ thymocytes in the human fetal-thymus organ culture (HF-TOC). We demonstrate that uninterrupted replication is required for continual thymocyte depletion. During depletion, NL4-R3A induces an increase in thymocytes which uptake 7AAD, a marker of cell death, and which express active caspase-3, a marker of apoptosis. While 7AAD uptake is observed predominantly in uninfected thymocytes (p24−), active caspase-3 is expressed in both infected (p24+) and uninfected thymocytes (p24−). When added to HF-TOC with ongoing infection, the protease inhibitor saquinavir efficiently suppresses NL4-R3A replication. In contrast, the fusion inhibitors T20 and C34 allow for sustained HIV-1 production. Interestingly, T20 and C34 effectively prevent thymocyte depletion in spite of this sustained replication. Apoptosis of both p24− and p24+ thymocytes appears to be envelope fusion dependent, as T20, but not saquinavir, is capable of reducing thymocyte apoptosis. Together, our data support a model whereby pathogenic envelope-dependent fusion contributes to thymocyte depletion in HIV-1-infected thymus, correlated with induction of apoptosis in both p24+ and p24− thymocytes.

scholarly journals Phosphorylation of Human Immunodeficiency Virus Type 1 Vpr Regulates Cell Cycle Arrest

2000 ◽  
Vol 74 (14) ◽  
pp. 6520-6527 ◽  
Author(s):  
Yi Zhou ◽  
Lee Ratner
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Cell Cycle Arrest ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Cell Cycle Progression ◽  
Cycle Arrest ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Vpr regulates nuclear transport of the viral preintegration complex, G2 cell cycle arrest, and transcriptional transactivation. We asked whether phosphorylation could affect Vpr activity. Vpr was found to be phosphorylated on serine residues in transiently transfected and infected cells. Residues 79, 94, and 96 were all found to be phosphorylated, as assessed by alanine mutations. Mutation of Ser-79 to Ala abrogated effects of Vpr on cell cycle progression, whereas mutation of Ser-94 and Ser-96 had no effect. Simultaneous mutation of all three Vpr serine residues attenuated HIV-1 replication in macrophages, whereas single and double Ser mutations had no effect.

scholarly journals Human Immunodeficiency Virus Type 1 Vpr Induces DNA Replication Stress InVitro and In Vivo

2006 ◽  
Vol 80 (21) ◽  
pp. 10407-10418 ◽  
Author(s):  
Erik S. Zimmerman ◽  
Michael P. Sherman ◽  
Jana L. Blackett ◽  
Jason A. Neidleman ◽  
Christophe Kreis ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Dependent Manner ◽  
Immunodeficiency Virus ◽  
Atr Activation ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) causes cell cycle arrest in G2. Vpr-expressing cells display the hallmarks of certain forms of DNA damage, specifically activation of the ataxia telangiectasia mutated and Rad3-related kinase, ATR. However, evidence that Vpr function is relevant in vivo or in the context of viral infection is still lacking. In the present study, we demonstrate that HIV-1 infection of primary, human CD4+ lymphocytes causes G2 arrest in a Vpr-dependent manner and that this response requires ATR, as shown by RNA interference. The event leading to ATR activation in CD4+ lymphocytes is the accumulation of replication protein A in nuclear foci, an indication that Vpr likely induces stalling of replication forks. Primary macrophages are refractory to ATR activation by Vpr, a finding that is consistent with the lack of detectable ATR, Rad17, and Chk1 protein expression in these nondividing cells. These observations begin to explain the remarkable resilience of macrophages to HIV-1-induced cytopathicity. To study the in vivo consequences of Vpr function, we isolated CD4+ lymphocytes from HIV-1-infected individuals and interrogated the cell cycle status of anti-p24Gag-immunoreactive cells. We report that infected cells in vivo display an aberrant cell cycle profile whereby a majority of cells have a 4N DNA content, consistent with the onset of G2 arrest.

scholarly journals Human Immunodeficiency Virus Type 1 Induction Mediated by Genistein Is Linked to Cell Cycle Arrest in G2

1998 ◽  
Vol 72 (10) ◽  
pp. 8174-8180 ◽  
Author(s):  
Joel Gozlan ◽  
Janet L. Lathey ◽  
Stephen A. Spector
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Cell Differentiation ◽  
Tyrosine Kinase ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Immunodeficiency Virus ◽  
P24 Antigen ◽  
Hiv 1

ABSTRACT Protein tyrosine kinase (PTK) phosphorylation is involved in cellular proliferation and differentiation processes that are key factors for human immunodeficiency virus type 1 (HIV-1) regulation in infected monocytic cells. Short-term exposure of the chronically infected promyelocytic OM10 cell line with the PTK inhibitor genistein induced a dose-dependent increase in p24 antigen production in culture supernatants. This induction persisted in the presence of the reverse transcriptase inhibitor, zidovudine, and was associated with an increased transcription of HIV-1 multiply spliced and unspliced RNAs, suggesting a transcriptional mechanism targeting the integrated provirus. Genistein induced cell differentiation, apoptosis, and a G2 arrest in the OM10 cells. Cell differentiation and apoptosis were not directly involved in the observed increase in HIV-1 replication that was closely linked to genistein-induced G2 arrest. Alleviation of the G2 arrest by pentoxyfylline resulted in a concomitant reduction of HIV-1 to baseline replication. Additionally, by flow cytometry, a significant increase in the number of p24 antigen-expressing cells was observed in cells arrested in G2 compared to those located in G1 or S. Tyrosine kinase inhibition was found not to be essential for enhanced viral replication, which seemed to be related to two other properties of genistein, inhibition of topoisomerase II activity and inhibition of phosphotidylinositol turnover. These findings are consistent with the recent observation that HIV-1 Vpr induces viral replication through preventing proliferation of cells by arresting them in G2 of the cell cycle and strongly suggest that manipulation of the cell cycle plays an important role in HIV-1 pathogenesis.

scholarly journals Delayed Human Immunodeficiency Virus Type 1-Induced Apoptosis in Cells Expressing Truncated Forms of CD4

1998 ◽  
Vol 72 (3) ◽  
pp. 1754-1761 ◽  
Author(s):  
Claire Guillerm ◽  
Nolwenn Coudronnière ◽  
Véronique Robert-Hebmann ◽  
Christian Devaux
Keyword(s):  
Human Immunodeficiency Virus ◽  
Cell Death ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Antigen Expression ◽  
Immunodeficiency Virus ◽  
Virus Exposure ◽  
Induced Apoptosis ◽  
Hiv 1

ABSTRACT It has been reported previously that cells expressing a truncated form of CD4 which lacks the cytoplasmic tail of the molecule (truncation at position 402) were not sensitive to human immunodeficiency virus type 1 (HIV-1)-induced apoptosis in an acute-phase model of infection (J. Corbeil, M. Tremblay, and D. D. Richman, J. Exp. Med. 183:39–48, 1996). The role played by the cytoplasmic domain of CD4 in HIV-1-induced apoptosis was reexamined here with clones of A2.01 cells expressing different forms of CD4 and the DNA intercalant YOPRO-1 assay. Six days after virus exposure, we found evidence of apoptosis in A2.01 cells expressing the wild-type CD4 (A2.01/CD4), whereas enhanced apoptosis remained absent in cultures of A2.01/CD4.401 and A2.01/CD4.403 cells (A2.01 cells which express CD4.401 and CD4.403 molecules with truncations at positions 401 and 403, respectively). However, cell death by apoptosis measured with YOPRO-1 was found in cultures of A2.01/CD4.401 and A2.01/CD4.403 cells 15 days after virus exposure. This result was confirmed with a terminal dUTP nick end-labeling assay and propidium iodide staining. The long lag time postinfection required for apoptosis to be observed in cultures of infected cells expressing truncated forms of CD4 was due to the delayed viral replication in these cells, as shown by monitoring of the viral reverse transcriptase activity and HIV-1 p24 gag antigen expression. These results emphasize the relationship between virus replication and cell death by apoptosis.

scholarly journals DDB1 and Cul4A Are Required for Human Immunodeficiency Virus Type 1 Vpr-Induced G2 Arrest

2007 ◽  
Vol 81 (19) ◽  
pp. 10822-10830 ◽  
Author(s):  
Lindi Tan ◽  
Elana Ehrlich ◽  
Xiao-Fang Yu
Keyword(s):  
Cell Cycle ◽  
Human Immunodeficiency Virus ◽  
Cell Cycle Arrest ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Sirna Treatment ◽  
Cycle Arrest ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Vpr-mediated induction of G2 cell cycle arrest has been postulated to be important for human immunodeficiency virus type 1 (HIV-1) replication, but the precise role of Vpr in this cell cycle arrest is unclear. In the present study, we have shown that HIV-1 Vpr interacts with damaged DNA binding protein 1 (DDB1) but not its partner DDB2. The interaction of Vpr with DDB1 was inhibited when DCAF1 (VprBP) expression was reduced by short interfering RNA (siRNA) treatment. The Vpr mutant (Q65R) that was defective for DCAF1 interaction also had a defect in DDB1 binding. However, Vpr binding to DDB1 was not sufficient to induce G2 arrest. A reduction in DDB1 or DDB2 expression in the absence of Vpr also did not induce G2 arrest. On the other hand, Vpr-induced G2 arrest was impaired when the intracellular level of DDB1 or Cullin 4A was reduced by siRNA treatment. Furthermore, Vpr-induced G2 arrest was largely abolished by a proteasome inhibitor. These data suggest that Vpr assembles with DDB1 through interaction with DCAF1 to form an E3 ubiquitin ligase that targets cellular substrates for proteasome-mediated degradation and G2 arrest.

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