scholarly journals Elucidating the Role of HIV-2 Viral Protein X

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 24
Author(s):  
Mohamed Mahdi ◽  
Tamás Richárd Linkner ◽  
Zsófia Ilona Szojka ◽  
József Tőzsér
Keyword(s):  
Viral Protein ◽  
Nuclear Export ◽  
Dual Infection ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
In Vitro Assays ◽  
Accessory Protein ◽  
Protein X ◽  
Hiv 1

Human immunodeficiency viruses type 1 and 2 (HIV-1 and HIV-2) are the causative agents of the acquired immunodeficiency syndrome (AIDS). While both viruses share a similar structural and genomic organization, a difference in replication dynamics and the clinical course of infection is evident between the two. Patients dually infected were shown to have lower viral loads and generally a slower rate of progression to AIDS than those who are mono-infected. While the roles of the unique accessory proteins have been studied in detail for HIV-1, those of HIV-2, including viral protein X (Vpx), remain largely uncharacterized. In our previous experiments, Vpx of HIV-2 was found to be involved in decreasing the infectivity of HIV-1 in dual infection cell culture assays. We set out to elucidate the function of this accessory protein, identifying protein–protein interactions of HIV-2 Vpx with cellular and possibly HIV-1 proteins in dual infection, using in-vitro proteomics techniques and proximity ligation assays. Results showed that wild-type Vpx interacted with many cellular proteins involved in splicing, packaging of pre-mRNA, nuclear export, and translation. Of particular interest was the interaction between HIV-2 Vpx and the pre-mRNA-splicing factor ATP-dependent RNA helicase DHX15, which is required for HIV-1 viral DNA synthesis, and the eukaryotic translation initiation factor 2 subunit 3 (EIF2S3), involved in the early steps of protein synthesis. Additionally, Vpx was found to interact directly with the cellular transcriptional repressor C-Terminal Binding Protein 2 (CTBP-2). Moreover, Vpx was shown to hinder the function of HIV-1 reverse transcriptase in in-vitro assays. These findings shed light on the functions of this accessory protein and add to our understanding of the replication dynamics of HIV-2 and its role in dual infection.

scholarly journals CBP80/20-dependent translation initiation factor (CTIF) inhibits HIV-1 Gag synthesis by targeting the function of the viral protein Rev

2019 ◽  
Author(s):  
Francisco García-de-Gracia ◽  
Daniela Toro-Ascuy ◽  
Sebastián Riquelme-Barrios ◽  
Camila Pereira-Montecinos ◽  
Bárbara Rojas-Araya ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Viral Protein ◽  
Nuclear Export ◽  
Ribosomal Subunit ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Viral Transcript ◽  
40S Ribosomal Subunit ◽  
Cellular Mrnas ◽  
Hiv 1

ABSTRACTTranslation initiation of the human immunodeficiency virus type-1 (HIV-1) unspliced mRNA has been shown to occur through cap-dependent and IRES-driven mechanisms. Previous studies suggested that the nuclear cap-binding complex (CBC) rather than eIF4E drives cap-dependent translation of the unspliced mRNA and we have recently reported that the CBC subunit CBP80 supports the function of the viral protein Rev during nuclear export and translation of this viral transcript. Ribosome recruitment during CBC-dependent translation of cellular mRNAs relies on the activity CBP80/20 translation initiation factor (CTIF), which bridges CBP80 and the 40S ribosomal subunit through interactions with eIF3g. Here, we report that CTIF restricts HIV-1 replication by interfering with Gag synthesis from the unspliced mRNA. Our results indicate that CTIF associates with Rev through its N-terminal domain and is recruited onto the unspliced mRNA ribonucleoprotein complex in order to block translation. We also demonstrate that CTIF induces the cytoplasmic accumulation of Rev impeding the association of the viral protein with CBP80. We finally show that CTIF restricts HIV-2 but not MLV Gag synthesis indicating an inhibitory mechanism conserved in Rev-expressing human lentiviruses.

scholarly journals ADAR1 and PACT contribute to efficient translation of transcripts containing HIV-1 trans-activating response (TAR) element

2017 ◽  
Vol 474 (7) ◽  
pp. 1241-1257 ◽  
Author(s):  
Evelyn Chukwurah ◽  
Indhira Handy ◽  
Rekha C. Patel
Keyword(s):  
Viral Proteins ◽  
Antiviral Response ◽  
Cellular Protein ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Protein Activator ◽  
Cellular Antiviral Response ◽  
Innate Antiviral Response ◽  
Hiv 1

Human immunodeficiency virus type 1 (HIV-1) has evolved various measures to counter the host cell's innate antiviral response during the course of infection. Interferon (IFN)-stimulated gene products are produced following HIV-1 infection to limit viral replication, but viral proteins and RNAs counteract their effect. One such mechanism is specifically directed against the IFN-induced Protein Kinase PKR, which is centrally important to the cellular antiviral response. In the presence of viral RNAs, PKR is activated and phosphorylates the translation initiation factor eIF2α. This shuts down the synthesis of both host and viral proteins, allowing the cell to mount an effective antiviral response. PACT (protein activator of PKR) is a cellular protein activator of PKR, primarily functioning to activate PKR in response to cellular stress. Recent studies have indicated that during HIV-1 infection, PACT's normal cellular function is compromised and that PACT is unable to activate PKR. Using various reporter systems and in vitro kinase assays, we establish in this report that interactions between PACT, ADAR1 and HIV-1-encoded Tat protein diminish the activation of PKR in response to HIV-1 infection. Our results highlight an important pathway by which HIV-1 transcripts subvert the host cell's antiviral activities to enhance their translation.

scholarly journals Cofactor Requirements for Nuclear Export of Rev Response Element (Rre)–And Constitutive Transport Element (Cte)–Containing Retroviral Rnas

2001 ◽  
Vol 152 (5) ◽  
pp. 895-910 ◽  
Author(s):  
Wilma Hofmann ◽  
Beate Reichart ◽  
Andrea Ewald ◽  
Eleonora Müller ◽  
Iris Schmitt ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Kinase Inhibitor ◽  
Initiation Factor ◽  
Nuclear Pore ◽  
Xenopus Laevis Oocytes ◽  
Binding Studies ◽  
Rev Response Element ◽  
Constitutive Transport Element ◽  
Hiv 1

Nuclear export of proteins containing leucine-rich nuclear export signals (NESs) is mediated by the export receptor CRM1/exportin1. However, additional protein factors interacting with leucine-rich NESs have been described. Here, we investigate human immunodeficiency virus type 1 (HIV-1) Rev-mediated nuclear export and Mason-Pfizer monkey virus (MPMV) constitutive transport element (CTE)–mediated nuclear export in microinjected Xenopus laevis oocytes. We show that eukaryotic initiation factor 5A (eIF-5A) is essential for Rev and Rev-mediated viral RNA export, but not for nuclear export of CTE RNA. In vitro binding studies demonstrate that eIF-5A is required for efficient interaction of Rev–NES with CRM1/exportin1 and that eIF-5A interacts with the nucleoporins CAN/nup214, nup153, nup98, and nup62. Quite unexpectedly, nuclear actin was also identified as an eIF-5A binding protein. We show that actin is associated with the nucleoplasmic filaments of nuclear pore complexes and is critically involved in export processes. Finally, actin- and energy-dependent nuclear export of HIV-1 Rev is reconstituted by using a novel in vitro egg extract system. In summary, our data provide evidence that actin plays an important functional role in nuclear export not only of retroviral RNAs but also of host proteins such as protein kinase inhibitor (PKI).

scholarly journals Venetoclax response is enhanced by selective inhibitor of nuclear export compounds in hematologic malignancies

2020 ◽  
Vol 4 (3) ◽  
pp. 586-598 ◽  
Author(s):  
Melissa A. Fischer ◽  
Sharon Y. Friedlander ◽  
Maria P. Arrate ◽  
Hua Chang ◽  
Agnieszka E. Gorska ◽  
...  
Keyword(s):  
Nuclear Export ◽  
B Cell Lymphoma ◽  
Hematologic Malignancies ◽  
Selective Inhibitor ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Messenger Rnas ◽  
Dlbcl Patient ◽  
Cytoplasmic Transport

Abstract The selective inhibitor of nuclear export (SINE) compounds selinexor (KPT-330) and eltanexor (KPT-8602) are from a novel class of small molecules that target exportin-1 (XPO1 [CRM1]), an essential nucleo-cytoplasmic transport protein responsible for the nuclear export of major tumor suppressor proteins and growth regulators such as p53, p21, and p27. XPO1 also affects the translation of messenger RNAs for critical oncogenes, including MYC, BCL2, MCL1, and BCL6, by blocking the export of the translation initiation factor eIF4E. Early trials with venetoclax (ABT-199), a potent, selective inhibitor of BCL2, have revealed responses across a variety of hematologic malignancies. However, many tumors are not responsive to venetoclax. We used models of acute myeloid leukemia (AML) and diffuse large B-cell lymphoma (DLBCL) to determine in vitro and in vivo responses to treatment with venetoclax and SINE compounds combined. Cotreatment with venetoclax and SINE compounds demonstrated loss of viability in multiple cell lines. Further in vitro analyses showed that this enhanced cell death was the result of an increase in apoptosis that led to a loss of clonogenicity in methylcellulose assays, coinciding with activation of p53 and loss of MCL1. Treatment with SINE compounds and venetoclax combined led to a reduction in tumor growth in both AML and DLBCL xenografts. Immunohistochemical analysis of tissue sections revealed that the reduction in tumor cells was partly the result of an induction of apoptosis. The enhanced effects of this combination were validated in primary AML and DLBCL patient cells. Our studies reveal synergy with SINE compounds and venetoclax in aggressive hematologic malignancies and provide a rationale for pursuing this approach in a clinical trial.

scholarly journals CBP80/20-dependent translation initiation factor (CTIF) inhibits HIV-1 Gag synthesis by targeting the function of the viral protein Rev

RNA Biology ◽  
2020 ◽  
pp. 1-14
Author(s):  
Francisco García-de-Gracia ◽  
Aracelly Gaete-Argel ◽  
Sebastián Riquelme-Barrios ◽  
Camila Pereira-Montecinos ◽  
Bárbara Rojas-Araya ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Viral Protein ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Hiv 1

scholarly journals Inhibitory Effects of HIV-2 Vpx on Replication of HIV-1

2018 ◽  
Vol 92 (14) ◽  
Author(s):  
Mohamed Mahdi ◽  
Zsófia Szojka ◽  
János András Mótyán ◽  
József Tőzsér
Keyword(s):  
Cell Culture ◽  
Human Immunodeficiency Virus ◽  
Viral Protein ◽  
Dual Infection ◽  
Cellular Level ◽  
Potential Candidate ◽  
Accessory Gene ◽  
Immunodeficiency Virus ◽  
Protein X ◽  
Hiv 1

ABSTRACTHuman immunodeficiency virus type 1 (HIV-1) and HIV-2 share a striking genomic resemblance; however, variability in the genetic sequence accounts for the presence of unique accessory genes, such as the viral protein X (vpx) gene in HIV-2. Dual infection with both viruses has long been described in the literature, yet the molecular mechanism of how dually infected patients tend to do better than those who are monoinfected with HIV-1 has not yet been explored. We hypothesized that in addition to extracellular mechanisms, an HIV-2 accessory gene is the culprit, and interference at the viral accessory/regulatory protein level is perhaps responsible for the attenuated pathogenicity of HIV-1 observed in dually infected patients. Following simulation of dual infection in cell culture experiments, we found that pretransduction of cells with HIV-2 significantly protects against HIV-1 transduction. Importantly, we have found that this dampening of the infectivity of HIV-1 was a result of interviral interference carried out by viral protein X of HIV-2, resulting in a severe hindrance to the replication dynamics of HIV-1, influencing both its early and late phases of the viral life cycle. Our findings shed light on potential intracellular interactions between the two viruses and broaden our understanding of the observed clinical spectrum in dually infected patients, highlighting HIV-2 Vpx as a potential candidate worth exploring in the fight against HIV-1.IMPORTANCEDual infection with human immunodeficiency virus types 1 and 2 is relatively common in areas of endemicity. For as-yet-unclarified reasons, patients who are dually infected were shown to have lower viral loads and generally a lower rate of progression to AIDS than those who are monoinfected. We aimed to explore dual infection in cell culture, to elucidate possible mechanisms by which HIV-2 may be able to exert such an effect. Our results indicate that on the cellular level, pretransduction of cells with HIV-2 significantly protects against HIV-1 transduction, which was found to be a result of interviral interference carried out by viral protein X of HIV-2. These findings broaden our knowledge of interviral interactions on the cellular level and may provide an explanation for the decreased pathogenicity of HIV-1 in dually infected patients, highlighting HIV-2 Vpx as a potential candidate worth exploring in the fight against HIV.

scholarly journals Central domain of a potyvirus VPg is involved in the interaction with the host translation initiation factor eIF4E and the viral protein HcPro

2007 ◽  
Vol 88 (3) ◽  
pp. 1029-1033 ◽  
Author(s):  
G. Roudet-Tavert ◽  
T. Michon ◽  
J. Walter ◽  
T. Delaunay ◽  
E. Redondo ◽  
...  
Keyword(s):  
Amino Acids ◽  
Recombinant Proteins ◽  
Translation Initiation ◽  
Viral Protein ◽  
Binding Protein ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Biological Functions ◽  
Central Domain

Using recombinant proteins produced in bacteria or in infected plants, interactions between the VPg and HcPro of Lettuce mosaic potyvirus (LMV) and between LMV VPg and the lettuce translation initiation factor 4E, the cap-binding protein (eIF4E), were demonstrated in vitro. Interaction with eIF4E and HcPro both involved the same VPg central domain. The structure of this domain in the VPg context was predicted to include an amphiphilic α-helix, with the amino acids related to biological functions in various potyviruses exposed at the hydrophilic side.

Discovery of N-Phenyl-4-(1H-pyrrol-3-yl)pyrimidin-2-amine Derivatives as Potent Mnk2 Inhibitors: Design, Synthesis, SAR Analysis, and Evaluation of in vitro Anti-leukaemic Activity

2019 ◽  
Vol 15 (6) ◽  
pp. 602-623 ◽  
Author(s):  
Ahmed M. Abdelaziz ◽  
Sarah Diab ◽  
Saiful Islam ◽  
Sunita K.C. Basnet ◽  
Benjamin Noll ◽  
...  
Keyword(s):  
Proliferative Activity ◽  
Myeloid Cell ◽  
Structural Diversity ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cell Leukaemia ◽  
Aberrant Expression ◽  
Design Synthesis ◽  
Induced Apoptosis

Background:Aberrant expression of eukaryotic translation initiation factor 4E (eIF4E) is common in many types of cancer including acute myeloid leukaemia (AML). Phosphorylation of eIF4E by MAPK-interacting kinases (Mnks) is essential for the eIF4E-mediated oncogenic activity. As such, the pharmacological inhibition of Mnks can be an effective strategy for the treatment of cancer.Methods:A series of N-phenyl-4-(1H-pyrrol-3-yl)pyrimidin-2-amine derivatives was designed and synthesised. The Mnk inhibitory activity of these derivatives as well as their anti-proliferative activity against MV4-11 AML cells was determined.Results:These compounds were identified as potent Mnk2 inhibitors. Most of them demonstrated potent anti-proliferative activity against MV4-11 AML cells. The cellular mechanistic studies of the representative inhibitors revealed that they reduced the level of phosphorylated eIF4E and induced apoptosis by down-regulating the anti-apoptotic protein myeloid cell leukaemia 1 (Mcl-1) and by cleaving poly(ADP-ribose)polymerase (PARP). The lead compound 7k possessed desirable pharmacokinetic properties and oral bioavailability.Conclusion:This work proposes that exploration of the structural diversity in the context of Nphenyl- 4-(1H-pyrrol-3-yl)pyrimidin-2-amine would offer potent and selective Mnk inhibitors.

scholarly journals Circadian clock control of eIF2α phosphorylation is necessary for rhythmic translation initiation

2020 ◽  
Vol 117 (20) ◽  
pp. 10935-10945 ◽  
Author(s):  
Shanta Karki ◽  
Kathrina Castillo ◽  
Zhaolan Ding ◽  
Olivia Kerr ◽  
Teresa M. Lamb ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Nutrient Metabolism ◽  
Eif2α Phosphorylation ◽  
Eif2α Kinase ◽  
The Impact

The circadian clock in eukaryotes controls transcriptional and posttranscriptional events, including regulation of the levels and phosphorylation state of translation factors. However, the mechanisms underlying clock control of translation initiation, and the impact of this potential regulation on rhythmic protein synthesis, were not known. We show that inhibitory phosphorylation of eIF2α (P-eIF2α), a conserved translation initiation factor, is clock controlled in Neurospora crassa, peaking during the subjective day. Cycling P-eIF2α levels required rhythmic activation of the eIF2α kinase CPC-3 (the homolog of yeast and mammalian GCN2), and rhythmic activation of CPC-3 was abolished under conditions in which the levels of charged tRNAs were altered. Clock-controlled accumulation of P-eIF2α led to reduced translation during the day in vitro and was necessary for the rhythmic synthesis of select proteins in vivo. Finally, loss of rhythmic P-eIF2α levels led to reduced linear growth rates, supporting the idea that partitioning translation to specific times of day provides a growth advantage to the organism. Together, these results reveal a fundamental mechanism by which the clock regulates rhythmic protein production, and provide key insights into how rhythmic translation, cellular energy, stress, and nutrient metabolism are linked through the levels of charged versus uncharged tRNAs.

scholarly journals Dual modulation of Ras-Mnk and PI3K-AKT-mTOR pathways: A Novel c-FLIP inhibitory mechanism of 3-AWA mediated translational attenuation through dephosphorylation of eIF4E

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Reyaz ur Rasool ◽  
Bilal Rah ◽  
Hina Amin ◽  
Debasis Nayak ◽  
Souneek Chakraborty ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Cell Cycle Progression ◽  
De Novo ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Apoptosis Resistance ◽  
Nih3t3 Cells ◽  
Eukaryotic Translation ◽  
Underlying Mechanisms

Abstract The eukaryotic translation initiation factor 4E (eIF4E) is considered as a key survival protein involved in cell cycle progression, transformation and apoptosis resistance. Herein, we demonstrate that medicinal plant derivative 3-AWA (from Withaferin A) suppressed the proliferation and metastasis of CaP cells through abrogation of eIF4E activation and expression via c-FLIP dependent mechanism. This translational attenuation prevents the de novo synthesis of major players of metastatic cascades viz. c-FLIP, c-Myc and cyclin D1. Moreover, the suppression of c-FLIP due to inhibition of translation initiation complex by 3-AWA enhanced FAS trafficking, BID and caspase 8 cleavage. Further ectopically restored c-Myc and GFP-HRas mediated activation of eIF4E was reduced by 3-AWA in transformed NIH3T3 cells. Detailed underlying mechanisms revealed that 3-AWA inhibited Ras-Mnk and PI3-AKT-mTOR, two major pathways through which eIF4E converges upon eIF4F hub. In addition to in vitro studies, we confirmed that 3-AWA efficiently suppressed tumor growth and metastasis in different mouse models. Given that 3-AWA inhibits c-FLIP through abrogation of translation initiation by co-targeting mTOR and Mnk-eIF4E, it (3-AWA) can be exploited as a lead pharmacophore for promising anti-cancer therapeutic development.

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