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Kleinberger T. Biology of the adenovirus E4orf4 protein: from virus infection to cancer cell death. FEBS Lett 2019; 594:1891-1917. [DOI: 10.1002/1873-3468.13704] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 11/24/2019] [Accepted: 11/25/2019] [Indexed: 12/14/2022]
Affiliation(s)
- Tamar Kleinberger
- Department of Molecular Microbiology the Rappaport Faculty of Medicine Technion –Israel Institute of Technology Haifa Israel
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2
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Cancer Treatment Goes Viral: Using Viral Proteins to Induce Tumour-Specific Cell Death. Cancers (Basel) 2019; 11:cancers11121975. [PMID: 31817939 PMCID: PMC6966515 DOI: 10.3390/cancers11121975] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/04/2019] [Accepted: 12/05/2019] [Indexed: 12/24/2022] Open
Abstract
Cell death is a tightly regulated process which can be exploited in cancer treatment to drive the killing of the tumour. Several conventional cancer therapies including chemotherapeutic agents target pathways involved in cell death, yet they often fail due to the lack of selectivity they have for tumour cells over healthy cells. Over the past decade, research has demonstrated the existence of numerous proteins which have an intrinsic tumour-specific toxicity, several of which originate from viruses. These tumour-selective viral proteins, although from distinct backgrounds, have several similar and interesting properties. Though the mechanism(s) of action of these proteins are not fully understood, it is possible that they can manipulate several cell death modes in cancer exemplifying the intricate interplay between these pathways. This review will discuss our current knowledge on the topic and outstanding questions, as well as deliberate the potential for viral proteins to progress into the clinic as successful cancer therapeutics.
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3
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Colle JH, Périchon B, Garcia A. Antitumor and antibacterial properties of virally encoded cationic sequences. Biologics 2019; 13:117-126. [PMID: 31417238 PMCID: PMC6599856 DOI: 10.2147/btt.s201287] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Accepted: 03/22/2019] [Indexed: 11/30/2022]
Abstract
Objective: The objective of this study was to test our Viral Quinta Columna Strategy (VQCS), a new biological hypothesis predicting that specific multifunctional virally encoded cationic domains may have the capacity to penetrate human cells and interact with PP2A proteins to deregulate important human intracellular pathways, and may display LL37 cathelicidin-like antagonistic effects against multiple pathogens such as bacteria or viruses. Methods: We comparatively analyzed the host defense properties of adenodiaphorins and of some specific cationic sequences encoded by different viruses using two distinct biological models: U87G, a well-characterized cell tumor model; and a group B Streptococcus agalactiae NEM316 ΔdltA, highly sensitive to LL37 cathelicidin. Results: We found that the adenovirus type 2 E4orf4 is a cell-permeable protein containing a new E4orf464–95 protein transduction domain, named large adenodiaphorin or LadD64–95. Interestingly, the host defense LL37 peptide is the unique cathelicidin in humans. In this context, we also demonstrated that similarly to LL37 LadD64–95, several virally encoded cationic sequences including the C-terminus HIV-1 89.6 Vpr77–92, shorter adenodiaphorins AdD67–84/AdD/69–84/AdD69–83, as well as HIV-2 Tat67–90 and JC polyomavirus small t115–134, displayed similar toxicity against Gram-positive S. agalactiae NEM316 ΔdltA strain. Finally, LadD64–95, adenodiaphorin AdD67–84, AdD69–84, and LL37 and LL17–32 cathelicidin peptides also inhibited the survival of human U87G glioblastoma cells. Conclusion: In this study, we demonstrated that specific cationic sequences encoded by four different viruses displayed antibacterial activities against S. agalactiae NEM316 ΔdltA strain. In addition, HIV-1 Vpr71–92 and adenovirus 2 E4orf464–95, two cationic penetrating sequences that bind PP2A, inhibited the survival of U87G glioblastoma cells. These results illustrate the host defense properties of virally encoded sequences and could represent an initial step for future complete validation of the VQCS hypothesis.
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Affiliation(s)
- Jean-Hervé Colle
- Laboratoire E3 des Phosphatases-Unité RMN, Institut Pasteur, Paris, France
| | - Bruno Périchon
- Unité de Biologie des Bactéries pathogènes à Gram-positif, Institut Pasteur, Paris, France
| | - Alphonse Garcia
- Laboratoire E3 des Phosphatases-Unité RMN, Institut Pasteur, Paris, France.,Département de Biologie Structurale et Chimie et pôle Dde-Design de la Biologie, Institut Pasteur, Paris, France
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4
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Hall DT, Griss T, Ma JF, Sanchez BJ, Sadek J, Tremblay AMK, Mubaid S, Omer A, Ford RJ, Bedard N, Pause A, Wing SS, Di Marco S, Steinberg GR, Jones RG, Gallouzi IE. The AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), but not metformin, prevents inflammation-associated cachectic muscle wasting. EMBO Mol Med 2019; 10:emmm.201708307. [PMID: 29844217 PMCID: PMC6034131 DOI: 10.15252/emmm.201708307] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Activation of AMPK has been associated with pro-atrophic signaling in muscle. However, AMPK also has anti-inflammatory effects, suggesting that in cachexia, a syndrome of inflammatory-driven muscle wasting, AMPK activation could be beneficial. Here we show that the AMPK agonist AICAR suppresses IFNγ/TNFα-induced atrophy, while the mitochondrial inhibitor metformin does not. IFNγ/TNFα impair mitochondrial oxidative respiration in myotubes and promote a metabolic shift to aerobic glycolysis, similarly to metformin. In contrast, AICAR partially restored metabolic function. The effects of AICAR were prevented by the AMPK inhibitor Compound C and were reproduced with A-769662, a specific AMPK activator. AICAR and A-769662 co-treatment was found to be synergistic, suggesting that the anti-cachectic effects of these drugs are mediated through AMPK activation. AICAR spared muscle mass in mouse models of cancer and LPS induced atrophy. Together, our findings suggest a dual function for AMPK during inflammation-driven atrophy, wherein it can play a protective role when activated exogenously early in disease progression, but may contribute to anabolic suppression and atrophy when activated later through mitochondrial dysfunction and subsequent metabolic stress.
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Affiliation(s)
- Derek T Hall
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Takla Griss
- Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada.,Department of Physiology, McGill University, Montreal, QC, Canada
| | - Jennifer F Ma
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Brenda Janice Sanchez
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Jason Sadek
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Anne Marie K Tremblay
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Souad Mubaid
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Amr Omer
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Rebecca J Ford
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - Nathalie Bedard
- Department of Medicine, McGill University and the Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Arnim Pause
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Simon S Wing
- Department of Medicine, McGill University and the Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Sergio Di Marco
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada
| | - Gregory R Steinberg
- Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - Russell G Jones
- Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada.,Department of Physiology, McGill University, Montreal, QC, Canada
| | - Imed-Eddine Gallouzi
- Department of Biochemistry, McGill University, Montreal, QC, Canada .,Rosalind and Morris Goodman Cancer Centre, Montreal, QC, Canada.,Life Sciences Division, College of Sciences and Engineering, Hamad Bin Khalifa University (HBKU), Doha, Qatar
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5
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Lobaina Y, Perera Y. Implication of B23/NPM1 in Viral Infections, Potential Uses of B23/NPM1 Inhibitors as Antiviral Therapy. Infect Disord Drug Targets 2019; 19:2-16. [PMID: 29589547 DOI: 10.2174/1871526518666180327124412] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 01/08/2018] [Accepted: 02/12/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND B23/nucleophosmin (B23/NPM1) is an abundant multifunctional protein mainly located in the nucleolus but constantly shuttling between the nucleus and cytosol. As a consequence of its constitutive expression, intracellular dynamics and binding capacities, B23/NPM1 interacts with multiple cellular factors in different cellular compartments, but also with viral proteins from both DNA and RNA viruses. B23/NPM1 influences overall viral replication of viruses like HIV, HBV, HCV, HDV and HPV by playing functional roles in different stages of viral replication including nuclear import, viral genome transcription and assembly, as well as final particle formation. Of note, some virus modify the subcellular localization, stability and/or increases B23/NPM1 expression levels on target cells, probably to foster B23/NPM1 functions in their own replicative cycle. RESULTS This review summarizes current knowledge concerning the interaction of B23/NPM1 with several viral proteins during relevant human infections. The opportunities and challenges of targeting this well-conserved host protein as a potentially new broad antiviral treatment are discussed in detail. Importantly, although initially conceived to treat cancer, a handful of B23/NPM1 inhibitors are currently available to test on viral infection models. CONCLUSION As B23/NPM1 partakes in key steps of viral replication and some viral infections remain as unsolved medical needs, an appealing idea may be the expedite evaluation of B23/NPM1 inhibitors in viral infections. Furthermore, worth to be addressed is if the up-regulation of B23/NPM1 protein levels that follows persistent viral infections may be instrumental to the malignant transformation induced by virus like HBV and HCV.
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Affiliation(s)
- Yadira Lobaina
- Therapeutic Hepatitis B Vaccine Group, Vaccine Division, Biomedical Research Direction, Center for Genetic Engineering and Biotechnology, Havana, CP 10600, Cuba
| | - Yasser Perera
- Molecular Oncology Group, Pharmaceuticals Division, Biomedical Research Direction, Center for Genetic Engineering and Biotechnology, Havana, CP 10600, Cuba
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6
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Abstract
Small viral proteins with cationic domains can be involved in multiple biological processes including cell penetration or interaction with intracellular targets. Within the last two decades several reports indicated that the C-terminus of HIV-1 Vpr is a cell penetrating sequence, a PP2A-dependent death domain and also displays toxicity against Gram-negative E. coli. Interestingly, HIV-1 Vpr, as well as some cationic proteins encoded by different viruses, share similar physical properties with the unique anti-microbial human cathelicidin LL37 peptide. Consistent with these observations, the Viral Quinta Columna Hypothesis predicts that virally-encoded cationic peptides encoded by multiple viruses may at the same time i) behave as new cathelicidin-like viral positive effectors of innate immunity, mainly through electrostatic interactions with microbial walls, and also display specific toxic cellular effects through interactions with specific intracellular targets such as PP2A proteins. In this context, virally-encoded cationic peptides, potentially detectable in biological fluids, may define a new paradigm for a viral control of homeostasis. Finally, we can also predict that characterization of virally encoded sequences with anti-infective effects may serve as template for the design of new efficient therapeutics polypeptides.
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Affiliation(s)
- Alphonse Garcia
- Laboratoire E3 Phosphatases, Unité RMN, Institut Pasteur, 25 rue du Dr. Roux, 75015 Paris, France.
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The Human Adenovirus Type 5 E4orf4 Protein Targets Two Phosphatase Regulators of the Hippo Signaling Pathway. J Virol 2015; 89:8855-70. [PMID: 26085163 DOI: 10.1128/jvi.03710-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 06/05/2015] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED When expressed alone at high levels, the human adenovirus E4orf4 protein exhibits tumor cell-specific p53-independent toxicity. A major E4orf4 target is the B55 class of PP2A regulatory subunits, and we have shown recently that binding of E4orf4 inhibits PP2A(B55) phosphatase activity in a dose-dependent fashion by preventing access of substrates (M. Z. Mui et al., PLoS Pathog 9:e1003742, 2013, http://dx.doi.org/10.1371/journal.ppat.1003742). While interaction with B55 subunits is essential for toxicity, E4orf4 mutants exist that, despite binding B55 at high levels, are defective in cell killing, suggesting that other essential targets exist. In an attempt to identify additional targets, we undertook a proteomics approach to characterize E4orf4-interacting proteins. Our findings indicated that, in addition to PP2A(B55) subunits, ASPP-PP1 complex subunits were found among the major E4orf4-binding species. Both the PP2A and ASPP-PP1 phosphatases are known to positively regulate effectors of the Hippo signaling pathway, which controls the expression of cell growth/survival genes by dephosphorylating the YAP transcriptional coactivator. We find here that expression of E4orf4 results in hyperphosphorylation of YAP, suggesting that Hippo signaling is affected by E4orf4 interactions with PP2A(B55) and/or ASPP-PP1 phosphatases. Furthermore, knockdown of YAP1 expression was seen to enhance E4orf4 killing, again consistent with a link between E4orf4 toxicity and inhibition of the Hippo pathway. This effect may in fact contribute to the cancer cell specificity of E4orf4 toxicity, as many human cancer cells rely heavily on the Hippo pathway for their enhanced proliferation. IMPORTANCE The human adenovirus E4orf4 protein has been known for some time to induce tumor cell-specific death when expressed at high levels; thus, knowledge of its mode of action could be of importance for development of new cancer therapies. Although the B55 form of the phosphatase PP2A has long been known as an essential E4orf4 target, genetic analyses indicated that others must exist. To identify additional E4orf4 targets, we performed, for the first time, a large-scale affinity purification/mass spectrometry analysis of E4orf4 binding partners. Several additional candidates were detected, including key regulators of the Hippo signaling pathway, which enhances cell viability in many cancers, and results of preliminary studies suggested a link between inhibition of Hippo signaling and E4orf4 toxicity.
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Kleinberger T. Mechanisms of cancer cell killing by the adenovirus E4orf4 protein. Viruses 2015; 7:2334-57. [PMID: 25961489 PMCID: PMC4452909 DOI: 10.3390/v7052334] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 04/23/2015] [Accepted: 04/30/2015] [Indexed: 12/24/2022] Open
Abstract
During adenovirus (Ad) replication the Ad E4orf4 protein regulates progression from the early to the late phase of infection. However, when E4orf4 is expressed alone outside the context of the virus it induces a non-canonical mode of programmed cell death, which feeds into known cell death pathways such as apoptosis or necrosis, depending on the cell line tested. E4orf4-induced cell death has many interesting and unique features including a higher susceptibility of cancer cells to E4orf4-induced cell killing compared with normal cells, caspase-independence, a high degree of evolutionary conservation of the signaling pathways, a link to perturbations of the cell cycle, and involvement of two distinct cell death programs, in the nucleus and in the cytoplasm. Several E4orf4-interacting proteins including its major partners, protein phosphatase 2A (PP2A) and Src family kinases, contribute to induction of cell death. The various features of E4orf4-induced cell killing as well as studies to decipher the underlying mechanisms are described here. Many explanations for the cancer specificity of E4orf4-induced cell death have been proposed, but a full understanding of the reasons for the different susceptibility of cancer and normal cells to killing by E4orf4 will require a more detailed analysis of the complex E4orf4 signaling network. An improved understanding of the mechanisms involved in this unique mode of programmed cell death may aid in design of novel E4orf4-based cancer therapeutics.
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Affiliation(s)
- Tamar Kleinberger
- Department of Microbiology, Faculty of Medicine, Technion-Israel Institute of Technology, 1 Efron St., Bat Galim, Haifa 31096, Israel.
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Interregional Coevolution Analysis Revealing Functional and Structural Interrelatedness between Different Genomic Regions in Human Mastadenovirus D. J Virol 2015; 89:6209-17. [PMID: 25833048 DOI: 10.1128/jvi.00515-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 03/25/2015] [Indexed: 01/22/2023] Open
Abstract
UNLABELLED Human mastadenovirus D (HAdV-D) is exceptionally rich in type among the seven human adenovirus species. This feature is attributed to frequent intertypic recombination events that have reshuffled orthologous genomic regions between different HAdV-D types. However, this trend appears to be paradoxical, as it has been demonstrated that the replacement of some of the interacting proteins for a specific function with other orthologues causes malfunction, indicating that intertypic recombination events may be deleterious. In order to understand why the paradoxical trend has been possible in HAdV-D evolution, we conducted an interregional coevolution analysis between different genomic regions of 45 different HAdV-D types and found that ca. 70% of the genome has coevolved, even though these are fragmented into several pieces via short intertypic recombination hot spot regions. Since it is statistically and biologically unlikely that all of the coevolving fragments have synchronously recombined between different genomes, it is probable that these regions have stayed in their original genomes during evolution as a platform for frequent intertypic recombination events in limited regions. It is also unlikely that the same genomic regions have remained almost untouched during frequent recombination events, independently, in all different types, by chance. In addition, the coevolving regions contain the coding regions of physically interacting proteins for important functions. Therefore, the coevolution of these regions should be attributed at least in part to natural selection due to common biological constraints operating on all types, including protein-protein interactions for essential functions. Our results predict additional unknown protein interactions. IMPORTANCE Human mastadenovirus D, an exceptionally type-rich human adenovirus species and causative agent of different diseases in a wide variety of tissues, including that of ocular region and digestive tract, as well as an opportunistic infection in immunocompromised patients, is known to have highly diverged through frequent intertypic recombination events; however, it has also been demonstrated that the replacement of a component protein of a multiprotein system with a homologous protein causes malfunction. The present study solved this apparent paradox by looking at which genomic parts have coevolved using a newly developed method. The results revealed that intertypic recombination events have occurred in limited genomic regions and been avoided in the genomic regions encoding proteins that physically interact for a given function. This approach detects purifying selection against recombination events causing the replacement of partial components of multiprotein systems and therefore predicts physical and functional interactions between different proteins and/or genomic elements.
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Gupta SK, Gandham RK, Sahoo AP, Tiwari AK. Viral genes as oncolytic agents for cancer therapy. Cell Mol Life Sci 2015; 72:1073-94. [PMID: 25408521 PMCID: PMC11113997 DOI: 10.1007/s00018-014-1782-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Revised: 10/29/2014] [Accepted: 11/13/2014] [Indexed: 12/20/2022]
Abstract
Many viruses have the ability to modulate the apoptosis, and to accomplish it; viruses encode proteins which specifically interact with the cellular signaling pathways. While some viruses encode proteins, which inhibit the apoptosis or death of the infected cells, there are viruses whose encoded proteins can kill the infected cells by multiple mechanisms, including apoptosis. A particular class of these viruses has specific gene(s) in their genomes which, upon ectopic expression, can kill the tumor cells selectively without affecting the normal cells. These genes and their encoded products have demonstrated great potential to be developed as novel anticancer therapeutic agents which can specifically target and kill the cancer cells leaving the normal cells unharmed. In this review, we will discuss about the viral genes having specific cancer cell killing properties, what is known about their functioning, signaling pathways and their therapeutic applications as anticancer agents.
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Affiliation(s)
- Shishir Kumar Gupta
- Molecular Biology Lab, Division of Veterinary Biotechnology, Indian Veterinary Research Institute, Izatnagar, Bareilly, 243122 UP India
| | - Ravi Kumar Gandham
- Molecular Biology Lab, Division of Veterinary Biotechnology, Indian Veterinary Research Institute, Izatnagar, Bareilly, 243122 UP India
| | - A. P. Sahoo
- Molecular Biology Lab, Division of Veterinary Biotechnology, Indian Veterinary Research Institute, Izatnagar, Bareilly, 243122 UP India
| | - A. K. Tiwari
- Molecular Biology Lab, Division of Veterinary Biotechnology, Indian Veterinary Research Institute, Izatnagar, Bareilly, 243122 UP India
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Interaction of adenovirus type 5 E4orf4 with the nuclear pore subunit Nup205 is required for proper viral gene expression. J Virol 2014; 88:13249-59. [PMID: 25210169 DOI: 10.1128/jvi.00933-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Adenovirus type 5 E4orf4 is a multifunctional protein that regulates viral gene expression. The activities of E4orf4 are mainly mediated through binding to protein phosphatase 2A (PP2A). E4orf4 recruits target phosphoproteins into complexes with PP2A, resulting in dephosphorylation of host factors, such as SR splicing factors. In the current study, we utilized immunoprecipitation followed by mass spectrometry to identify novel E4orf4-interacting proteins. In this manner we identified Nup205, a component of the nuclear pore complex (NPC) as an E4orf4 interacting partner. The arginine-rich motif (ARM) of E4orf4 was required for interaction with Nup205 and for nuclear localization of E4orf4. ARMs are commonly found on viral nuclear proteins, and we observed that Nup205 interacts with three different nuclear viral proteins containing ARMs. E4orf4 formed a trimolecular complex containing both Nup205 and PP2A. Furthermore, Nup205 complexed with E4orf4 was hypophosphorylated, suggesting that the protein is specifically targeted for dephosphorylation. An adenovirus mutant that does not express E4orf4 (Orf4(-)) displayed elevated early and reduced late gene expression relative to that of the wild type. We observed that knockdown of Nup205 resulted in the same phenotype as that of the Orf4(-) virus, suggesting that the proteins function as a complex to regulate viral gene expression. Furthermore, knockdown of Nup205 resulted in a more than a 4-fold reduction in the replication of wild-type adenovirus. Our data show for first time that Ad5 E4orf4 interacts with and modifies the NPC and that Nup205-E4orf4 binding is required for normal regulation of viral gene expression and viral replication. IMPORTANCE Nuclear pore complexes (NPCs) are highly regulated conduits in the nuclear membrane that control transport of macromolecules between the nucleus and cytoplasm. Viruses that replicate in the nucleus must negotiate the NPC during nuclear entry, and viral DNA, mRNA, and proteins must then be exported from the nucleus. Several types of viruses restructure the NPC to facilitate replication, and the current study shows that adenovirus type 5 (Ad5) utilizes a novel mechanism to modify NPC function. We demonstrate that a subunit of the NPC, Nup205, is a phosphoprotein that is actively dephosphorylated by the Ad5-encoded protein E4orf4. Moreover, Nup205 is required by Ad5 to regulate viral gene expression and efficient viral replication. Nup205 is a nonstructural subunit that is responsible for the gating functions of the NPC, and this study suggests for the first time that the NPC is regulated by phosphorylation both during normal physiology and viral infection.
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12
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Kleinberger T. Induction of cancer-specific cell death by the adenovirus E4orf4 protein. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 818:61-97. [PMID: 25001532 DOI: 10.1007/978-1-4471-6458-6_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The adenovirus E4orf4 protein is a multifunctional viral regulator that contributes to temporal regulation of the progression of viral infection. When expressed alone, outside the context of the virus, E4orf4 induces p53-independent cell-death in transformed cells. Oncogenic transformation of primary cells in tissue culture sensitizes them to cell killing by E4orf4, indicating that E4orf4 research may have implications for cancer therapy. It has also been reported that E4orf4 induces a caspase-independent, non-classical apoptotic pathway, which maintains crosstalk with classical caspase-dependent pathways. Furthermore, several E4orf4 activities in the nucleus and in the cytoplasm and various protein partners contribute to cell killing by this viral protein. In the following chapter I summarize the current knowledge of the unique mode of E4orf4-induced cell death and its underlying mechanisms. Although several explanations for the cancer-specificity of E4orf4-induced toxicity have been proposed, a better grasp of the mechanisms responsible for E4orf4-induced cell death is required to elucidate the differential sensitivity of normal and cancer cells to E4orf4.
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Affiliation(s)
- Tamar Kleinberger
- Department of Molecular Microbiology, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, 31096, Israel,
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Mui MZ, Kucharski M, Miron MJ, Hur WS, Berghuis AM, Blanchette P, Branton PE. Identification of the adenovirus E4orf4 protein binding site on the B55α and Cdc55 regulatory subunits of PP2A: Implications for PP2A function, tumor cell killing and viral replication. PLoS Pathog 2013; 9:e1003742. [PMID: 24244166 PMCID: PMC3828177 DOI: 10.1371/journal.ppat.1003742] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 09/18/2013] [Indexed: 11/18/2022] Open
Abstract
Adenovirus E4orf4 protein induces the death of human cancer cells and Saccharomyces cerevisiae. Binding of E4orf4 to the B/B55/Cdc55 regulatory subunit of protein phosphatase 2A (PP2A) is required, and such binding inhibits PP2AB55 activity leading to dose-dependent cell death. We found that E4orf4 binds across the putative substrate binding groove predicted from the crystal structure of B55α such that the substrate p107 can no longer interact with PP2AB55α. We propose that E4orf4 inhibits PP2AB55 activity by preventing access of substrates and that at high E4orf4 levels this inhibition results in cell death through the failure to dephosphorylate substrates required for cell cycle progression. However, E4orf4 is expressed at much lower and less toxic levels during a normal adenovirus infection. We suggest that in this context E4orf4 largely serves to recruit novel substrates such as ASF/SF2/SRSF1 to PP2AB55 to enhance adenovirus replication. Thus E4orf4 toxicity probably represents an artifact of overexpression and does not reflect the evolutionary function of this viral product. The adenovirus E4orf4 protein when expressed alone at high levels induces the death of human cancer cells but not normal primary cells. It also is toxic in the yeast Saccharomyces cerevisiae, which we have used as a model system in some studies. Toxicity induced by the E4orf4 protein is largely dependent on its ability to associate with the highly conserved B/B55/Cdc55 class of regulatory subunits of protein phosphatase 2A (PP2A), of which the mammalian B55α species is best characterized structurally. We showed previously that binding to B55α appears to inhibit PP2A activity against at least some substrates. In the present study, we mapped the E4orf4 binding site on both yeast Cdc55 and mammalian B55α and propose how such binding may inhibit PP2A activity. The implications of E4orf4 binding on PP2A activity are of significant scientific interest in terms of the process by which PP2A recognizes and dephosphorylates its substrates. We also propose that E4orf4 binding in the context of viral replication serves the quite different function of introducing novel substrates for dephosphorylation by the PP2A holoenzyme.
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Affiliation(s)
- Melissa Z. Mui
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Michael Kucharski
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | | | - Woosuk Steve Hur
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | | | - Paola Blanchette
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
| | - Philip E. Branton
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
- Department of Oncology, McGill University, Montreal, Quebec, Canada
- The Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
- * E-mail:
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Adenovirus E4orf4 protein-induced death of p53-/- H1299 human cancer cells follows a G1 arrest of both tetraploid and diploid cells due to a failure to initiate DNA synthesis. J Virol 2013; 87:13168-78. [PMID: 24067978 DOI: 10.1128/jvi.01242-13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The adenovirus E4orf4 protein selectively kills human cancer cells independently of p53 and thus represents a potentially promising tool for the development of novel antitumor therapies. Previous studies suggested that E4orf4 induces an arrest or a delay in mitosis and that both this effect and subsequent cell death rely largely on an interaction with the B55 regulatory subunit of protein phosphatase 2A. In the present report, we show that the death of human H1299 lung carcinoma cells induced by expression of E4orf4 is typified not by an accumulation of cells arrested in mitosis but rather by the presence of both tetraploid and diploid cells that are arrested in G1 because they are unable to initiate DNA synthesis. We believe that these E4orf4-expressing cells eventually die by various processes, including those resulting from mitotic catastrophe.
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15
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Scott MS, Troshin PV, Barton GJ. NoD: a Nucleolar localization sequence detector for eukaryotic and viral proteins. BMC Bioinformatics 2011; 12:317. [PMID: 21812952 PMCID: PMC3166288 DOI: 10.1186/1471-2105-12-317] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 08/03/2011] [Indexed: 12/15/2022] Open
Abstract
Background Nucleolar localization sequences (NoLSs) are short targeting sequences responsible for the localization of proteins to the nucleolus. Given the large number of proteins experimentally detected in the nucleolus and the central role of this subnuclear compartment in the cell, NoLSs are likely to be important regulatory elements controlling cellular traffic. Although many proteins have been reported to contain NoLSs, the systematic characterization of this group of targeting motifs has only recently been carried out. Results Here, we describe NoD, a web server and a command line program that predicts the presence of NoLSs in proteins. Using the web server, users can submit protein sequences through the NoD input form and are provided with a graphical output of the NoLS score as a function of protein position. While the web server is most convenient for making prediction for just a few proteins, the command line version of NoD can return predictions for complete proteomes. NoD is based on our recently described human-trained artificial neural network predictor. Through stringent independent testing of the predictor using available experimentally validated NoLS-containing eukaryotic and viral proteins, the NoD sensitivity and positive predictive value were estimated to be 71% and 79% respectively. Conclusions NoD is the first tool to provide predictions of nucleolar localization sequences in diverse eukaryotes and viruses. NoD can be run interactively online at http://www.compbio.dundee.ac.uk/nod or downloaded to use locally.
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Affiliation(s)
- Michelle S Scott
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
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16
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Abstract
Recent advances in proteomics have been combined with traditional methods for isolation of nucleoli from mammalian and plant cells. This approach has confirmed the growing body of data showing a wide role for the nucleolus in eukaryotic cell biology beyond ribosome generation into many areas of cell function from regulation of the cell cycle, modulation of the cell stress response to innate immune responses. This has been reflected in the growing body of evidence that viruses specifically target the nucleolus by sequestering cellular nucleolar proteins or by targeting viral proteins to the nucleolus in order to maximise viral replication. This review covers those key areas and looks at the latest approaches using high‐throughput quantitative proteomics of the nucleolus in virus infected cells to gain an insight into the role of this fascinating compartment in viral infection.
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Affiliation(s)
- Julian A Hiscox
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK
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17
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Mittelman K, Ziv K, Maoz T, Kleinberger T. The cytosolic tail of the Golgi apyrase Ynd1 mediates E4orf4-induced toxicity in Saccharomyces cerevisiae. PLoS One 2010; 5:e15539. [PMID: 21124936 PMCID: PMC2989921 DOI: 10.1371/journal.pone.0015539] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Accepted: 10/13/2010] [Indexed: 11/18/2022] Open
Abstract
The adenovirus E4 open reading frame 4 (E4orf4) protein contributes to regulation of the progression of virus infection. When expressed individually, E4orf4 was shown to induce non-classical transformed cell-specific apoptosis in mammalian cells. At least some of the mechanisms underlying E4orf4-induced toxicity are conserved from yeast to mammals, including the requirement for an interaction of E4orf4 with protein phosphatase 2A (PP2A). A genetic screen in yeast revealed that the Golgi apyrase Ynd1 associates with E4orf4 and contributes to E4orf4-induced toxicity, independently of Ynd1 apyrase activity. Ynd1 and PP2A were shown to contribute additively to E4orf4-induced toxicity in yeast, and to interact genetically and physically. A mammalian orthologue of Ynd1 was shown to bind E4orf4 in mammalian cells, confirming the evolutionary conservation of this interaction. Here, we use mutation analysis to identify the cytosolic tail of Ynd1 as the protein domain required for mediation of the E4orf4 toxic signal and for the interaction with E4orf4. We also show that E4orf4 associates with cellular membranes in yeast and is localized at their cytoplasmic face. However, E4orf4 is membrane-associated even in the absence of Ynd1, suggesting that additional membrane proteins may mediate E4orf4 localization. Based on our results and on a previous report describing a collection of Ynd1 protein partners, we propose that the Ynd1 cytoplasmic tail acts as a scaffold, interacting with a multi-protein complex, whose targeting by E4orf4 leads to cell death.
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Affiliation(s)
- Karin Mittelman
- Department of Molecular Microbiology, Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel
| | - Keren Ziv
- Department of Molecular Microbiology, Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel
| | - Tsofnat Maoz
- Department of Molecular Microbiology, Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel
| | - Tamar Kleinberger
- Department of Molecular Microbiology, Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel
- * E-mail:
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18
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Genetic analysis of B55alpha/Cdc55 protein phosphatase 2A subunits: association with the adenovirus E4orf4 protein. J Virol 2010; 85:286-95. [PMID: 21047956 DOI: 10.1128/jvi.01381-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human adenovirus E4orf4 protein is toxic in both human tumor cells and Saccharomyces cerevisiae. Previous studies indicated that most of this toxicity is dependent on an interaction of E4orf4 protein with the B55 class of regulatory subunits of protein phosphatase 2A (PP2A) and in yeast with the B55 homolog Cdc55. We have found previously that E4orf4 inhibits PP2A activity against at least some substrates. In an attempt to understand the mechanism of this inhibition, we used a genetic approach to identify residues in the seven-bladed β-propeller proteins B55α and Cdc55 required for E4orf4 binding. In both cases, amino-terminal polypeptides composed only of blade 1 and at least part of blade 2 were found to bind E4orf4 and overexpression blocked E4orf4 toxicity in yeast. Furthermore, certain amino acid substitutions in blades 1 and 2 within full-length B55α and Cdc55 resulted in loss of E4orf4 binding. Recent mutational analysis has suggested that segments of blades 1 and 2 present on the top face of B55α form part of the "substrate-binding groove." Additionally, these segments are in close proximity to the catalytic C subunit of the PP2A holoenzyme. Thus, our results are consistent with the hypothesis that E4orf4 binding could affect the access of substrates, resulting in the failure to dephosphorylate some PP2A substrates.
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19
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Adenovirus protein E4orf4 induces premature APCCdc20 activation in Saccharomyces cerevisiae by a protein phosphatase 2A-dependent mechanism. J Virol 2010; 84:4798-809. [PMID: 20164229 DOI: 10.1128/jvi.02434-09] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein phosphatase 2A (PP2A) has been implicated in cell cycle progression and mitosis; however, the complexity of PP2A regulation via multiple B subunits makes its functional characterization a significant challenge. The human adenovirus protein E4orf4 has been found to induce both high Cdk1 activity and the accumulation of cells in G(2)/M in both mammalian and yeast cells, effects which are largely dependent on the B55/Cdc55 regulatory subunit of PP2A. Thus, E4orf4 represents a unique means by which the function of a specific form of PP2A can be delineated in vivo. In Saccharomyces cerevisiae, only two PP2A regulatory subunits exist, Cdc55 and Rts1. Here, we show that E4orf4-induced toxicity depends on a functional interaction with Cdc55. E4orf4 expression correlates with the inappropriate reduction of Pds1 and Scc1 in S-phase-arrested cells. The unscheduled loss of these proteins suggests the involvement of PP2A(Cdc55) in the regulation of the Cdc20 form of the anaphase-promoting complex (APC). Contrastingly, activity of the Hct1 form of the APC is not induced by E4orf4, as demonstrated by the observed stability of its substrates. We propose that E4orf4, being a Cdc55-specific inhibitor of PP2A, demonstrates the role of PP2A(Cdc55) in regulating APC(Cdc20) activity.
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20
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Lindsay AJ, McCaffrey MW. Myosin Vb localises to nucleoli and associates with the RNA polymerase I transcription complex. ACTA ACUST UNITED AC 2010; 66:1057-72. [PMID: 19610025 DOI: 10.1002/cm.20408] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
It is becoming increasingly clear that the mammalian class V myosins are involved in a wide range of cellular processes such as receptor trafficking, mRNA transport, myelination in oligodendrocytes and cell division. Using paralog-specific antibodies, we observed significant nuclear localisation for both myosin Va and myosin Vb. Myosin Vb was present in nucleoli where it co-localises with RNA polymerase I, and newly synthesised ribosomal RNA (rRNA), indicating that it may play a role in transcription. Indeed, its nucleolar pattern was altered upon treatment with RNA polymerase I inhibitors. In contrast, myosin Va is largely excluded from nucleoli and is unaffected by these inhibitors. Myosin Vb was also found to physically associate with RNA polymerase I and actin in co-immunoprecipitation experiments. We propose that myosin Vb serves a role in rRNA transcription.
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Affiliation(s)
- Andrew J Lindsay
- Molecular Cell Biology Laboratory, Department of Biochemistry, Biosciences Institute, University College Cork, Cork, Ireland
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21
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Lam YW, Evans VC, Heesom KJ, Lamond AI, Matthews DA. Proteomics analysis of the nucleolus in adenovirus-infected cells. Mol Cell Proteomics 2009; 9:117-30. [PMID: 19812395 PMCID: PMC2808258 DOI: 10.1074/mcp.m900338-mcp200] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Adenoviruses replicate primarily in the host cell nucleus, and it is well
established that adenovirus infection affects the structure and function of host
cell nucleoli in addition to coding for a number of nucleolar targeted viral
proteins. Here we used unbiased proteomics methods, including high throughput
mass spectrometry coupled with stable isotope labeling by amino acids in cell
culture (SILAC) and traditional two-dimensional gel electrophoresis, to identify
quantitative changes in the protein composition of the nucleolus during
adenovirus infection. Two-dimensional gel analysis revealed changes in six
proteins. By contrast, SILAC-based approaches identified 351 proteins with 24
proteins showing at least a 2-fold change after infection. Of those, four were
previously reported to have aberrant localization and/or functional relevance
during adenovirus infection. In total, 15 proteins identified as changing in
amount by proteomics methods were examined in infected cells using confocal
microscopy. Eleven of these proteins showed altered patterns of localization in
adenovirus-infected cells. Comparing our data with the effects of actinomycin D
on the nucleolar proteome revealed that adenovirus infection apparently
specifically targets a relatively small subset of nucleolar antigens at the time
point examined.
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Affiliation(s)
- Yun W Lam
- Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong, China
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22
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Localization and importance of the adenovirus E4orf4 protein during lytic infection. J Virol 2008; 83:1689-99. [PMID: 19073741 DOI: 10.1128/jvi.01703-08] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The human adenovirus type 5 (Ad5) E4orf4 product has been studied extensively although in most cases as expressed from vectors in the absence of other viral products. Thus, relatively little is known about its role in the context of an adenovirus infection. Although considerable earlier work had indicated that the E4orf4 protein is not essential for replication, a recent study using dl359, an Ad5 mutant believed to produce a nonfunctional E4orf4 protein, suggested that E4orf4 is essential for virus growth in primary small-airway epithelial cells (C. O'Shea, et al., EMBO J. 24:1211-1221, 2005). Hence, to examine further the role of E4orf4 during virus infection, we generated for the first time a set of E4orf4 virus mutants in a common Ad5 genetic background. Such mutant viruses included those that express E4orf4 proteins containing various individual point mutations, those defective entirely in E4orf4 expression, and a mutant expressing wild-type E4orf4 fused to the green fluorescent protein. E4orf4 protein was found to localize primarily in nuclear structures shown to be viral replication centers, in nucleoli, and in perinuclear bodies. Importantly, E4orf4 was shown not to be essential for virus growth in either human tumor or primary cells, at least in tissue culture. Unlike E4orf4-null virus, mutant dl359 appeared to exhibit a gain-of-function phenotype that impairs virus growth. The dl359 E4orf4 protein, which contains a large in-frame internal deletion, clustered in aggregates enriched in Hsp70 and proteasome components. In addition, the late viral mRNAs produced by dl359 accumulated abnormally in a nuclear punctate pattern. Altogether, our results indicate that E4orf4 protein is not essential for virus growth in culture and that expression of the dl359 E4orf4 product interferes with viral replication, presumably through interactions with structures in the nucleus.
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23
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Backendorf C, Visser AE, de Boer AG, Zimmerman R, Visser M, Voskamp P, Zhang YH, Noteborn M. Apoptin: therapeutic potential of an early sensor of carcinogenic transformation. Annu Rev Pharmacol Toxicol 2008; 48:143-69. [PMID: 17848136 DOI: 10.1146/annurev.pharmtox.48.121806.154910] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The avian virus-derived protein apoptin induces p53-independent apoptosis in a tumor-specific way. Apoptin acts as a multimeric complex and forms superstructures upon binding to DNA. In tumor cells, apoptin is phosphorylated and mainly nuclear, whereas in normal cells it is unphosphorylated, cytoplasmic, and becomes readily neutralized. Interestingly, apoptin phosphorylation, nuclear translocation, and apoptosis can transiently be induced in normal cells by cotransfecting SV40 large T oncogene, indicating that apoptin recognizes early stages of oncogenic transformation. In cancer cells, apoptin appears to recognize survival signals, which it is able to redirect into cell death impulses. Apoptin targets include DEDAF, Nur77, Nmi, Hippi, and the potential drug target APC1. Apoptin-transgenic mice and animal tumor models have revealed apoptin as a safe and efficient antitumor agent, resulting in significant tumor regression. Future antitumor therapies could use apoptin either as a therapeutic bullet or as an early sensor of druggable tumor-specific processes.
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Affiliation(s)
- Claude Backendorf
- Molecular Genetics, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
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24
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Tollefson AE, Ying B, Doronin K, Sidor PD, Wold WSM. Identification of a new human adenovirus protein encoded by a novel late l-strand transcription unit. J Virol 2007; 81:12918-26. [PMID: 17881437 PMCID: PMC2169129 DOI: 10.1128/jvi.01531-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A short open reading frame named the "U exon," located on the adenovirus (Ad) l-strand (for leftward transcription) between the early E3 region and the fiber gene, is conserved in mastadenoviruses. We have observed that Ad5 mutants with large deletions in E3 that infringe on the U exon display a mild growth defect, as well as an aberrant Ad E2 DNA-binding protein (DBP) intranuclear localization pattern and an apparent failure to organize replication centers during late infection. Mutants in which the U exon DNA is reconstructed have a reversed phenotype. Chow et al. (L. T. Chow et al., J. Mol. Biol. 134:265-303, 1979) described mRNAs initiating in the region of the U exon and spliced to downstream sequences in the late DBP mRNA leader and the DBP-coding region. We have cloned this mRNA (as cDNA) from Ad5 late mRNA; the predicted protein is 217 amino acids, initiating in the U exon and continuing in frame in the DBP leader and in the DBP-coding region but in a different reading frame from DBP. Polyclonal and monoclonal antibodies generated against the predicted U exon protein (UXP) showed that UXP is approximately 24K in size by immunoblot and is a late protein. At 18 to 24 h postinfection, UXP is strongly associated with nucleoli and is found throughout the nucleus; later, UXP is associated with the periphery of replication centers, suggesting a function relevant to Ad DNA replication or RNA transcription. UXP is expressed by all four species C Ads. When expressed in transient transfections, UXP complements the aberrant DBP localization pattern of UXP-negative Ad5 mutants. Our data indicate that UXP is a previously unrecognized protein derived from a novel late l-strand transcription unit.
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Affiliation(s)
- Ann E Tollefson
- Department of Molecular Microbiology and Immunology, St. Louis University Health Sciences Center, 1100 South Grand Blvd., St. Louis, MO 63104, USA
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25
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Matthews DA. Study of nucleolar localization of adenovirus core proteins. METHODS IN MOLECULAR MEDICINE 2007; 131:73-81. [PMID: 17656776 DOI: 10.1007/978-1-59745-277-9_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
This chapter describes the techniques used to study nucleolar-localized proteins. The chapter starts with cloning of viral proteins for expression in mammalian cells as fusion proteins to well-characterized tags such as enhanced green fluorescence protein (EGFP). This follows on to techniques for transient expression in mammalian cells and immunofluorescence techniques used to examine subcellular localization. Finally there is guidance on the types of antigens and metabolic features of the nucleolus that can be used as markers to confirm that the protein in question is indeed localized in the nucleolus and determine whether it affects gross rRNA synthesis.
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26
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Wang DM, Zhou Y, Xie HJ, Ma XL, Wang X, Chen H, Huang BR. Cytotoxicity of a recombinant fusion protein of adenovirus early region 4 open reading frame 4 (E4orf4) and human epidermal growth factor on p53-deficient tumor cells. Anticancer Drugs 2007; 17:527-37. [PMID: 16702809 DOI: 10.1097/00001813-200606000-00006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Adenovirus early region 4 open reading frame 4 (E4orf4) protein is a novel cell death factor that selectively induces p53-independent apoptosis in cancer cells, but not in normal human cells. This study presents an approach for inhibiting p53-deficient tumor cell growth by using protein-based E4orf4 that had been genetically fused to epidermal growth factor (EGF) to ensure selective targeting of EGF receptor-overexpressing tumor cells. EGF-E4orf4 enables binding onto the cell surface and is then internalized into Saos-2 cells. The success of the process had been demonstrated by immunofluorescence assay and confocal laser microscopy. After prolonged exposure, E4orf4 remained mostly in the nuclei. EGF-E4orf4 treatment of Saos-2 cells showed dose-dependent cytotoxicity. Nearly 50% of the Saos-2 cells were killed at a concentration of 250 nmol/l. In contrast, EGF-E4orf4 showed no significant inhibitory effect iresn primary cells of human umbilical vein endothelial cells. To confirm the ability of EGF-E4orf4 to induce apoptosis, DNA fragmentation was detected using BrdUTP end-labeling. Flow cytometric analysis revealed a significant increase of apoptotic cells in Saos-2 cells treated with EGF-E4orf4, but not in the case of cells cultured in plain medium (t=0.028, P<0.05). In conclusion, these preliminary results indicate that EGF-E4orf4 could show promise as a new reagent that is more efficient and less toxic in anti-cancer therapy.
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Affiliation(s)
- Dong-Mei Wang
- National Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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27
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Robert A, Smadja-Lamère N, Landry MC, Champagne C, Petrie R, Lamarche-Vane N, Hosoya H, Lavoie JN. Adenovirus E4orf4 hijacks rho GTPase-dependent actin dynamics to kill cells: a role for endosome-associated actin assembly. Mol Biol Cell 2006; 17:3329-44. [PMID: 16687574 PMCID: PMC1483059 DOI: 10.1091/mbc.e05-12-1146] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Revised: 04/12/2006] [Accepted: 04/27/2006] [Indexed: 11/11/2022] Open
Abstract
The adenovirus early region 4 ORF4 protein (E4orf4) triggers a novel death program that bypasses classical apoptotic pathways in human cancer cells. Deregulation of the cell cytoskeleton is a hallmark of E4orf4 killing that relies on Src family kinases and E4orf4 phosphorylation. However, the cytoskeletal targets of E4orf4 and their role in the death process are unknown. Here, we show that E4orf4 translocates to cytoplasmic sites and triggers the assembly of a peculiar juxtanuclear actin-myosin network that drives polarized blebbing and nuclear shrinkage. We found that E4orf4 activates the myosin II motor and triggers de novo actin polymerization in the perinuclear region, promoting endosomes recruitment to the sites of actin assembly. E4orf4-induced actin dynamics requires interaction with Src family kinases and involves a spatial regulation of the Rho GTPases pathways Cdc42/N-Wasp, RhoA/Rho kinase, and Rac1, which make distinct contributions. Remarkably, activation of the Rho GTPases is required for induction of apoptotic-like cell death. Furthermore, inhibition of actin dynamics per se dramatically impairs E4orf4 killing. This work provides strong support for a causal role for endosome-associated actin dynamics in E4orf4 killing and in the regulation of cancer cell fate.
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Affiliation(s)
- Amélie Robert
- *Centre de Recherche en Cancérologie de l’Université Laval, L’Hôtel-Dieu de Québec, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec G1R 2J6, Canada
| | - Nicolas Smadja-Lamère
- *Centre de Recherche en Cancérologie de l’Université Laval, L’Hôtel-Dieu de Québec, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec G1R 2J6, Canada
| | - Marie-Claude Landry
- *Centre de Recherche en Cancérologie de l’Université Laval, L’Hôtel-Dieu de Québec, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec G1R 2J6, Canada
| | - Claudia Champagne
- *Centre de Recherche en Cancérologie de l’Université Laval, L’Hôtel-Dieu de Québec, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec G1R 2J6, Canada
| | - Ryan Petrie
- Department of Anatomy and Cell Biology, McGill University, Montreal, Québec H3A 2B2, Canada; and
| | - Nathalie Lamarche-Vane
- Department of Anatomy and Cell Biology, McGill University, Montreal, Québec H3A 2B2, Canada; and
| | - Hiroshi Hosoya
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Josée N. Lavoie
- *Centre de Recherche en Cancérologie de l’Université Laval, L’Hôtel-Dieu de Québec, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec G1R 2J6, Canada
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