Molecular mimicry in inducing DNA damage between HIV-1 Vpr and the anticancer agent, cisplatin

1Department of Biology, College of Science and Technology, Temple University, Philadelphia, PA, USA.
Oncogene (Impact Factor: 8.46). 02/2008; 27(1):32-43. DOI: 10.1038/sj.onc.1210632
Source: PubMed


The human immunodeficiency virus type 1 (HIV-1) viral protein R (vpr) gene is an evolutionarily conserved gene among the primate lentiviruses. Several functions are attributed to Vpr including the ability to cause cell death, cell cycle arrest, apoptosis and DNA damage. The Vpr domain responsible for DNA damage as well as the mechanism(s) through which Vpr induces this damage is unknown. Using site-directed mutagenesis, we identified the helical domain II within Vpr (aa 37-50) as the region responsible for causing DNA damage. Interestingly, Vpr Delta(37-50) failed to cause cell cycle arrest or apoptosis, to induce Ku70 or Ku80 and to suppress tumor growth, but maintained its capability to activate the HIV-1 LTR, to localize to the nucleus and to promote nonhomologous end-joining. In addition, our cytogenetic data indicated that helical domain II induced chromosomal aberrations, which mimicked those induced by cisplatin, an anticancer agent. This novel molecular mimicry function of Vpr might lead to its potential therapeutic use as a tumor suppressor.

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    • "Plasmids pAS1B-HA-Vpr and pEGFP-N1-Vpr were obtained from Dr. S. Benichou [75]. The pcDNA3.1-Vpr was obtained from Dr. B. E. Sawaya [6]. The MAM marker construct, FH-PSS-1, was provided by Dr. O. Kuge [76]. "
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    ABSTRACT: Human immunodeficiency virus 1 (HIV-1) viral protein R (Vpr) has been shown to induce host cell death by increasing the permeability of mitochondrial outer membrane (MOM). The mechanism underlying the damage to the mitochondria by Vpr, however, is not clearly illustrated. In this study, Vpr that is introduced, via transient transfection or lentivirus infection, into the human embryonic kidney cell line HEK293, human CD4(+) T lymphoblast cell line SupT1, or human primary CD4(+) T cells serves as the model system to study the molecular mechanism of Vpr-mediated HIV-1 pathogenesis. The results show that Vpr injures MOM and causes a loss in membrane potential (MMP) by posttranscriptionally reducing the expression of mitofusin 2 (Mfn2) via VprBP-DDB1-CUL4A ubiquitin ligase complex, gradually weakening MOM, and increasing mitochondrial deformation. Vpr also markedly decreases cytoplasmic levels of dynamin-related protein 1 (DRP1) and increases bulging in mitochondria-associated membranes (MAM), the specific regions of endoplasmic reticulum (ER) which form physical contacts with the mitochondria. Overexpression of Mfn2 and DRP1 significantly decreased the loss of MMP and apoptotic cell death caused by Vpr. Furthermore, by employing time-lapse confocal fluorescence microscopy, we identify the transport of Vpr protein from the ER, via MAM to the mitochondria. Taken together, our results suggest that Vpr-mediated cellular damage may occur on an alternative protein transport pathway from the ER, via MAM to the mitochondria, which are modulated by Mfn2 and DRP1.
    Full-text · Article · Mar 2012 · PLoS ONE
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    • "Interestingly, Vpr Delta (37-50) failed to induce cell cycle arrest or apoptosis, or to induce Ku70 or Ku80 expression or suppress tumor growth. However, the peptide activated the HIV-1 LTR, resulting in its localization to the nucleus where it promoted nonhomologous end-joining [31]. C81 shares the αH2 domain with Vpr; thus, C81 may have the ability to induce DNA damage. "
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    ABSTRACT: The human immunodeficiency virus type 1 (HIV-1) accessory protein Vpr induces apoptosis after cell cycle arrest at the G2 phase in primate cells. We have reported previously that C81, a carboxy-terminally truncated form of Vpr, interferes with cell proliferation and results in apoptosis without G2 arrest. Here, we investigated whether this property of Vpr and C81 could be exploited for use as a potential anticancer agent. First, we demonstrated that C81 induced G1 arrest and apoptosis in all tumor cells tested. In contrast, Vpr resulted in G2 arrest and apoptosis in HeLa and 293 T cells. Vpr also suppressed the damaged-DNA-specific binding protein 1 (DDB1) in HepG2 cells, thereby inducing apoptosis without G2 arrest. G2 arrest was restored when DDB1 was overexpressed in cells that also expressed Vpr. Surprisingly, C81 induced G2 arrest when DDB1 was overexpressed in HepG2 cells, but not in HeLa or 293 T cells. Thus, the induction of Vpr- and C81-mediated cell cycle arrest appears to depend on the cell type, whereas apoptosis was observed in all tumor cells tested. Overall, Vpr and C81 have potential as novel therapeutic agents for treatment of cancer.
    Full-text · Article · Sep 2009 · Cancer Cell International
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    • "Kasahara et al., 2007). In addition, studies from many groups have demonstrated that Vpr mediates multiple functions, including nuclear import of the HIV-1 pre-integration complex (Jacquot et al., 2007), G 2 cell cycle arrest caused by the induction of the damage-specific DNAbinding protein 1 (DDB1) and the Cullin 4A (Cul4A) E3 ubiquitin ligase pathway (Le Rouzic et al., 2008), transactivation of both viral replication and host genes and induction of caspasedependent cellular apoptosis (Siddiqui et al., 2008). Most of these Vpr functions have been confirmed in in vitro systems. "
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    ABSTRACT: The lack of productive infection of neurons by HIV-1 suggests that the neuronal damage seen in AIDS patients with cognitive disorders is caused indirectly via viral and cellular proteins with neurotoxic activity. Among HIV-1 proteins, Vpr has been shown to deregulate expression of various important cytokines and inflammatory proteins in infected and uninfected cells. However, the mechanisms underlying these changes remain unclear. Here, we demonstrate that neurons can take up Vpr that is released into the supernatant of HIV-infected microglia. We also found that administration of recombinant Vpr (rVpr) to human neurons resulted in a slow but sustained elevation of intracellular calcium [Ca(2+)]i. Interestingly, our data also show that [Ca(2+)]i elevation by Vpr leads to ROS production and impairs glutamate signaling in neuronal cells. Vpr disturbs calcium homeostasis through downregulation of endogenous PMCA. Finally, we found that the permeability of the plasma membrane increases in neurons treated with Vpr. Therefore, we conclude that soluble Vpr is a major viral factor that causes a disturbance in neuronal communication leading to neuronal dysfunction. The outcome of these studies will advance the understanding of HIV-1 pathogenesis and will help in the development of new therapeutic approaches.
    Full-text · Article · Apr 2009 · Brain research
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