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Zou W, Imperiale MJ. Regulation of Virus Replication by BK Polyomavirus Small T Antigen. J Virol 2023; 97:e0007723. [PMID: 36916919 PMCID: PMC10062181 DOI: 10.1128/jvi.00077-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 02/20/2023] [Indexed: 03/16/2023] Open
Abstract
Polyomavirus small T antigen (tAg) plays important roles in regulating viral replication, the innate immune response, apoptosis, and transformation for SV40, Merkel cell polyomavirus (MCPyV), murine polyomavirus (MuPyV), and JC polyomavirus (JCPyV). However, the function of BK polyomavirus (BKPyV) tAg has been much less studied. Here, we constructed mutant viruses that do not express tAg, and we showed that, in contrast with other polyomaviruses, BKPyV tAg inhibits large T antigen (TAg) gene expression and viral DNA replication. However, this occurs only in an archetype viral background. We also observed that the transduction of cells with a lentivirus-expressing BKPyV tAg kills the cells. We further discovered that BKPyV tAg interacts not only with PP2A A and C subunits, as has been demonstrated for other polyomavirus tAg proteins, but also with PP2A B''' subunit members. Knocking down either of two B''' subunits, namely STRN or STRN3, mimics the phenotype of the tAg mutant virus. However, a virus containing a point mutation in the PP2A binding domain of tAg only partially affected virus TAg expression and DNA replication. These results indicate that BKPyV tAg downregulates viral gene expression and DNA replication and that this occurs in part through interactions with PP2A. IMPORTANCE BK polyomavirus is a virus that establishes a lifelong infection of the majority of people. The infection usually does not cause any clinical symptoms, but, in transplant recipients whose immune systems have been suppressed, unchecked virus replication can cause severe disease. In this study, we show that a viral protein called small T antigen is one of the ways that the virus can persist without high levels of replication. Understanding which factors control viral replication enhances our knowledge of the virus life cycle and could lead to potential interventions for these patients.
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Affiliation(s)
- Wei Zou
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
| | - Michael J. Imperiale
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
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Sarwar Z, Nabi N, Bhat SA, Gillani SQ, Reshi I, Un Nisa M, Adelmant G, Marto J, Andrabi S. Interaction of DBC1 with polyoma small T antigen promotes its degradation and negatively regulates tumorigenesis. J Biol Chem 2021; 298:101496. [PMID: 34921839 PMCID: PMC8784333 DOI: 10.1016/j.jbc.2021.101496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 11/09/2021] [Accepted: 12/10/2021] [Indexed: 12/05/2022] Open
Abstract
Deleted in Breast Cancer 1 (DBC1) is an important metabolic sensor. Previous studies have implicated DBC1 in various cellular functions, notably cell proliferation, apoptosis, histone modification, and adipogenesis. However, current reports about the role of DBC1 in tumorigenesis are controversial and designate DBC1 alternatively as a tumor suppressor or a tumor promoter. In the present study, we report that polyoma small T antigen (PyST) associates with DBC1 in mammalian cells, and this interaction leads to the posttranslational downregulation of DBC1 protein levels. When coexpressed, DBC1 overcomes PyST-induced mitotic arrest and promotes the exit of cells from mitosis. Using both transient and stable modes of PyST expression, we also show that cellular DBC1 is subjected to degradation by LKB1, a tumor suppressor and cellular energy sensor kinase, in an AMP kinase-independent manner. Moreover, LKB1 negatively regulates the phosphorylation as well as activity of the prosurvival kinase AKT1 through DBC1 and its downstream pseudokinase substrate, Tribbles 3 (TRB3). Using both transient transfection and stable cell line approaches as well as soft agar assay, we demonstrate that DBC1 has oncogenic potential. In conclusion, our study provides insight into a novel signaling axis that connects LKB1, DBC1, TRB3, and AKT1. We propose that the LKB1–DBC1–AKT1 signaling paradigm may have an important role in the regulation of cell cycle and apoptosis and consequently tumorigenesis.
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Affiliation(s)
- Zarka Sarwar
- Department of Biochemistry, University of Kashmir, Srinagar, India, 190006
| | - Nusrat Nabi
- Department of Biochemistry, University of Kashmir, Srinagar, India, 190006
| | - Sameer Ahmed Bhat
- Department of Biochemistry, University of Kashmir, Srinagar, India, 190006
| | | | - Irfana Reshi
- Department of Biochemistry, University of Kashmir, Srinagar, India, 190006
| | - Misbah Un Nisa
- Department of Biochemistry, University of Kashmir, Srinagar, India, 190006
| | - Guillaume Adelmant
- Blais Proteomics Centre, Dana Farber Cancer Institute, Harvard University, Boston, USA
| | - Jarrod Marto
- Blais Proteomics Centre, Dana Farber Cancer Institute, Harvard University, Boston, USA
| | - Shaida Andrabi
- Department of Biochemistry, University of Kashmir, Srinagar, India, 190006.
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DeCaprio JA. Molecular Pathogenesis of Merkel Cell Carcinoma. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2020; 16:69-91. [PMID: 33228463 DOI: 10.1146/annurev-pathmechdis-012419-032817] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin with two distinct etiologies. Clonal integration of Merkel cell polyomavirus DNA into the tumor genome with persistent expression of viral T antigens causes at least 60% of all MCC. UV damage leading to highly mutated genomes causes a nonviral form of MCC. Despite these distinct etiologies, both forms of MCC are similar in presentation, prognosis, and response to therapy. At least three oncogenic transcriptional programs feature prominently in both forms of MCC driven by the virus or by mutation. Both forms of MCC have a high proliferative growth rate with increased levels of cell cycle-dependent genes due to inactivation of the tumor suppressors RB and p53, a strong MYC signature due to MYCL activation by the virus or gene amplification, and an attenuated neuroendocrine differentiation program driven by the ATOH1 transcription factor.
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Affiliation(s)
- James A DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA; .,Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.,Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA
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Peters DK, Erickson KD, Garcea RL. Live Cell Microscopy of Murine Polyomavirus Subnuclear Replication Centers. Viruses 2020; 12:v12101123. [PMID: 33023278 PMCID: PMC7650712 DOI: 10.3390/v12101123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 09/22/2020] [Accepted: 09/30/2020] [Indexed: 01/24/2023] Open
Abstract
During polyomavirus (PyV) infection, host proteins localize to subnuclear domains, termed viral replication centers (VRCs), to mediate viral genome replication. Although the protein composition and spatial organization of VRCs have been described using high-resolution immunofluorescence microscopy, little is known about the temporal dynamics of VRC formation over the course of infection. We used live cell fluorescence microscopy to analyze VRC formation during murine PyV (MuPyV) infection of a mouse fibroblast cell line that constitutively expresses a GFP-tagged replication protein A complex subunit (GFP-RPA32). The RPA complex forms a heterotrimer (RPA70/32/14) that regulates cellular DNA replication and repair and is a known VRC component. We validated previous observations that GFP-RPA32 relocalized to sites of cellular DNA damage in uninfected cells and to VRCs in MuPyV-infected cells. We then used GFP-RPA32 as a marker of VRC formation and expansion during live cell microscopy of infected cells. VRC formation occurred at variable times post-infection, but the rate of VRC expansion was similar between cells. Additionally, we found that the early viral protein, small TAg (ST), was required for VRC expansion but not VRC formation, consistent with the role of ST in promoting efficient vDNA replication. These results demonstrate the dynamic nature of VRCs over the course of infection and establish an approach for analyzing viral replication in live cells.
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Affiliation(s)
- Douglas K. Peters
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA; (D.K.P.); (K.D.E.)
| | - Kimberly D. Erickson
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA; (D.K.P.); (K.D.E.)
| | - Robert L. Garcea
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309, USA; (D.K.P.); (K.D.E.)
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO 80309, USA
- Correspondence:
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Polyomavirus Small T Antigen Induces Apoptosis in Mammalian Cells through the UNC5B Pathway in a PP2A-Dependent Manner. J Virol 2020; 94:JVI.02187-19. [PMID: 32404521 DOI: 10.1128/jvi.02187-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 05/02/2020] [Indexed: 11/20/2022] Open
Abstract
UNC5B is a dependence receptor that promotes survival in the presence of its ligand, netrin-1, while inducing cell death in its absence. The receptor has an important role in the development of the nervous and vascular systems. It is also involved in the normal turnover of intestinal epithelium. Netrin-1 and UNC5B are deregulated in multiple cancers, including colorectal, neuroblastoma, and breast tumors. However, the detailed mechanism of UNC5B function is not fully understood. We have utilized the murine polyomavirus small T antigen (PyST) as a tool to study UNC5B-mediated apoptosis. PyST is known to induce mitotic arrest followed by extensive cell death in mammalian cells. Our results show that the expression of PyST increases mRNA levels of UNC5B by approximately 3-fold in osteosarcoma cells (U2OS) and also stabilizes UNC5B at the posttranslational level. Furthermore, UNC5B is upregulated predominantly in those cells that undergo mitotic arrest upon PyST expression. Interestingly, although its expression was previously reported to be regulated by p53, our data show that the increase in UNC5B levels by PyST is p53 independent. The posttranslational stabilization of UNC5B by PyST is regulated by the interaction of PyST with PP2A. We also show that netrin-1 expression, which is known to inhibit UNC5B apoptotic activity, promotes survival of PyST-expressing cells. Our results thus suggest an important role of UNC5B in small-T antigen-induced mitotic catastrophe that also requires PP2A.IMPORTANCE UNC5B, PP2A, and netrin-1 are deregulated in a variety of cancers. UNC5B and PP2A are regarded as tumor suppressors, as they promote apoptosis and are deleted or mutated in many cancers. In contrast, netrin-1 promotes survival by inhibiting dependence receptors, including UNC5B, and is upregulated in many cancers. Here, we show that UNC5B-mediated apoptosis can occur independently of p53 but in a PP2A-dependent manner. A substantial percentage of cancers arise due to p53 mutations and are insensitive to chemotherapeutic treatments that activate p53. Unexpectedly, treatment of cancers having functional p53 with many conventional drugs leads to the upregulation of netrin-1 through activated p53, which is counterintuitive. Therefore, understanding the p53-independent mechanisms of the netrin-UNC5B axis, such as those involving PP2A, assumes greater clinical significance. Anticancer strategies utilizing anti-netrin-1 antibody treatment are already in clinical trials.
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Peters DK, Garcea RL. Murine polyomavirus DNA transitions through spatially distinct nuclear replication subdomains during infection. PLoS Pathog 2020; 16:e1008403. [PMID: 32203554 PMCID: PMC7117779 DOI: 10.1371/journal.ppat.1008403] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 04/02/2020] [Accepted: 02/13/2020] [Indexed: 12/16/2022] Open
Abstract
The replication of small DNA viruses requires both host DNA replication and repair factors that are often recruited to subnuclear domains termed viral replication centers (VRCs). Aside from serving as a spatial focus for viral replication, little is known about these dynamic areas in the nucleus. We investigated the organization and function of VRCs during murine polyomavirus (MuPyV) infection using 3D structured illumination microscopy (3D-SIM). We localized MuPyV replication center components, such as the viral large T-antigen (LT) and the cellular replication protein A (RPA), to spatially distinct subdomains within VRCs. We found that viral DNA (vDNA) trafficked sequentially through these subdomains post-synthesis, suggesting their distinct functional roles in vDNA processing. Additionally, we observed disruption of VRC organization and vDNA trafficking during mutant MuPyV infections or inhibition of DNA synthesis. These results reveal a dynamic organization of VRC components that coordinates virus replication.
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Affiliation(s)
- Douglas K. Peters
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, United States of America
| | - Robert L. Garcea
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, United States of America
- BioFrontiers Institute, University of Colorado Boulder, Boulder, Colorado, United States of America
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Horníková L, Bruštíková K, Forstová J. Microtubules in Polyomavirus Infection. Viruses 2020; 12:E121. [PMID: 31963741 PMCID: PMC7019765 DOI: 10.3390/v12010121] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 01/15/2020] [Accepted: 01/16/2020] [Indexed: 12/12/2022] Open
Abstract
Microtubules, part of the cytoskeleton, are indispensable for intracellular movement, cell division, and maintaining cell shape and polarity. In addition, microtubules play an important role in viral infection. In this review, we summarize the role of the microtubules' network during polyomavirus infection. Polyomaviruses usurp microtubules and their motors to travel via early and late acidic endosomes to the endoplasmic reticulum. As shown for SV40, kinesin-1 and microtubules are engaged in the release of partially disassembled virus from the endoplasmic reticulum to the cytosol, and dynein apparently assists in the further disassembly of virions prior to their translocation to the cell nucleus-the place of their replication. Polyomavirus gene products affect the regulation of microtubule dynamics. Early T antigens destabilize microtubules and cause aberrant mitosis. The role of these activities in tumorigenesis has been documented. However, its importance for productive infection remains elusive. On the other hand, in the late phase of infection, the major capsid protein, VP1, of the mouse polyomavirus, counteracts T-antigen-induced destabilization. It physically binds microtubules and stabilizes them. The interaction results in the G2/M block of the cell cycle and prolonged S phase, which is apparently required for successful completion of the viral replication cycle.
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Affiliation(s)
| | | | - Jitka Forstová
- Department of Genetics and Microbiology, Faculty of Science, Charles University, BIOCEV, 25250 Vestec, Czech Republic; (L.H.); (K.B.)
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DeCaprio JA. Merkel cell polyomavirus and Merkel cell carcinoma. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0276. [PMID: 28893943 DOI: 10.1098/rstb.2016.0276] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/09/2017] [Indexed: 12/27/2022] Open
Abstract
Merkel cell polyomavirus (MCPyV) causes the highly aggressive and relatively rare skin cancer known as Merkel cell carcinoma (MCC). MCPyV also causes a lifelong yet relatively innocuous infection and is one of 14 distinct human polyomaviruses species. Although polyomaviruses typically do not cause illness in healthy individuals, several can cause catastrophic diseases in immunocompromised hosts. MCPyV is the only polyomavirus clearly associated with human cancer. How MCPyV causes MCC and what oncogenic events must transpire to enable this virus to cause MCC is the focus of this essay.This article is part of the themed issue 'Human oncogenic viruses'.
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Affiliation(s)
- James A DeCaprio
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Boston, MA 02215, USA .,Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 450 Brookline Avenue, Boston, MA 02215, USA
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9
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Transformation by Polyomavirus Middle T Antigen Involves a Unique Bimodal Interaction with the Hippo Effector YAP. J Virol 2016; 90:7032-7045. [PMID: 27194756 PMCID: PMC4984622 DOI: 10.1128/jvi.00417-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/10/2016] [Indexed: 01/07/2023] Open
Abstract
UNLABELLED Murine polyomavirus has repeatedly provided insights into tumorigenesis, revealing key control mechanisms such as tyrosine phosphorylation and phosphoinositide 3-kinase (PI3K) signaling. We recently demonstrated that polyomavirus small T antigen (ST) binds YAP, a major effector of Hippo signaling, to regulate differentiation. Here we characterize YAP as a target of middle T antigen (MT) important for transformation. Through a surface including residues R103 and D182, wild-type MT binds to the YAP WW domains. Mutation of either R103 or D182 of MT abrogates YAP binding without affecting binding to other signaling molecules or the strength of PI3K or Ras signaling. Either genetic abrogation of YAP binding to MT or silencing of YAP via short hairpin RNA (shRNA) reduced MT transformation, suggesting that YAP makes a positive contribution to the transformed phenotype. MT targets YAP both by activating signaling pathways that affect it and by binding to it. MT signaling, whether from wild-type MT or the YAP-binding MT mutant, promoted YAP phosphorylation at S127 and S381/397 (YAP2/YAP1). Consistent with the known functions of these phosphorylated serines, MT signaling leads to the loss of YAP from the nucleus and degradation. Binding of YAP to MT brings it together with protein phosphatase 2A (PP2A), leading to the dephosphorylation of YAP in the MT complex. It also leads to the enrichment of YAP in membranes. Taken together, these results indicate that YAP promotes MT transformation via mechanisms that may depart from YAP's canonical oncogenic transcriptional activation functions. IMPORTANCE The highly conserved Hippo/YAP pathway is important for tissue development and homeostasis. Increasingly, changes in this pathway are being associated with cancer. Middle T antigen (MT) is the primary polyomavirus oncogene responsible for tumor formation. In this study, we show that MT signaling promotes YAP phosphorylation, loss from the nucleus, and increased turnover. Notably, MT genetics demonstrate that YAP binding to MT is important for transformation. Because MT also binds PP2A, YAP bound to MT is dephosphorylated, stabilized, and localized to membranes. Taken together, these results indicate that YAP promotes MT transformation via mechanisms that depart from YAP's canonical oncogenic transcriptional activation functions.
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Emerging differential roles of the pRb tumor suppressor in trichodysplasia spinulosa-associated polyomavirus and Merkel cell polyomavirus pathogeneses. J Clin Virol 2016; 76:40-3. [DOI: 10.1016/j.jcv.2016.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 12/21/2015] [Accepted: 01/05/2016] [Indexed: 01/13/2023]
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Expression of the small T antigen of Lymphotropic Papovavirus is sufficient to transform primary mouse embryo fibroblasts. Virology 2015; 487:112-20. [PMID: 26517398 DOI: 10.1016/j.virol.2015.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/25/2015] [Accepted: 10/02/2015] [Indexed: 01/17/2023]
Abstract
Polyomaviruses induce cell proliferation and transformation through different oncoproteins encoded within the early region (ER): large T antigen (LT), small T antigen (sT) and, in some cases, additional components. Each virus utilizes different mechanisms to achieve transformation. For instance, the LTs of Simian virus 40 (SV40), BK and/or JC virus can induce transformation; but Merkel Cell Polyomavirus (MCPyV) requires expression of sT. Lymphotropic Papovavirus (LPV) is closely related to Human Polyomavirus 9 (HuPyV9) and, under similar conditions, mice expressing LPV.ER exhibit higher rates of tumor formation than mice expressing SV40.ER. We have investigated the contributions of individual LPV.ER components to cell transformation. In contrast to SV40, LPV.ER transforms mouse embryonic fibroblasts (MEFs), but expression of LPV LT is insufficient to transform MEFs. Furthermore, LPV sT induces immortalization and transformation of MEFs. Thus, in the case of LPV, sT is the main mediator of oncogenesis.
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Garren SB, Kondaveeti Y, Duff MO, Carmichael GG. Global Analysis of Mouse Polyomavirus Infection Reveals Dynamic Regulation of Viral and Host Gene Expression and Promiscuous Viral RNA Editing. PLoS Pathog 2015; 11:e1005166. [PMID: 26407100 PMCID: PMC4583464 DOI: 10.1371/journal.ppat.1005166] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/24/2015] [Indexed: 12/15/2022] Open
Abstract
Mouse polyomavirus (MPyV) lytically infects mouse cells, transforms rat cells in culture, and is highly oncogenic in rodents. We have used deep sequencing to follow MPyV infection of mouse NIH3T6 cells at various times after infection and analyzed both the viral and cellular transcriptomes. Alignment of sequencing reads to the viral genome illustrated the transcriptional profile of the early-to-late switch with both early-strand and late-strand RNAs being transcribed at all time points. A number of novel insights into viral gene expression emerged from these studies, including the demonstration of widespread RNA editing of viral transcripts at late times in infection. By late times in infection, 359 host genes were seen to be significantly upregulated and 857 were downregulated. Gene ontology analysis indicated transcripts involved in translation, metabolism, RNA processing, DNA methylation, and protein turnover were upregulated while transcripts involved in extracellular adhesion, cytoskeleton, zinc finger binding, SH3 domain, and GTPase activation were downregulated. The levels of a number of long noncoding RNAs were also altered. The long noncoding RNA MALAT1, which is involved in splicing speckles and used as a marker in many late-stage cancers, was noticeably downregulated, while several other abundant noncoding RNAs were strongly upregulated. We discuss these results in light of what is currently known about the MPyV life cycle and its effects on host cell growth and metabolism. Mouse polyomavirus (MPyV) is a small 5.3kb circular double-stranded DNA virus capable of causing tumors in a variety of tissues in immunocompromised mice. It has been a subject of study for over 60 years, yielding insights into a number of processes including tumorigenesis, cell cycle signaling, and transformation. This study serves to provide a global view of the MPyV infection by utilizing Illumina sequencing to observe changes in total RNA from both the virus and the host cell as well as applying new methods to more directly confirm the extent of A-to-I editing of viral RNA by host ADAR enzymes. This allows for a simultaneous observation of both host and viral transcriptional changes that occur as a result of early gene expression and the viral switch from early to late genes that occurs coincident with the initiation of DNA replication.
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Affiliation(s)
- Seth B. Garren
- Department of Genetics and Genome Sciences, UCONN Health, Farmington, Connecticut, United States of America
| | - Yuvabharath Kondaveeti
- Department of Genetics and Genome Sciences, UCONN Health, Farmington, Connecticut, United States of America
| | - Michael O. Duff
- Department of Genetics and Genome Sciences, UCONN Health, Farmington, Connecticut, United States of America
| | - Gordon G. Carmichael
- Department of Genetics and Genome Sciences, UCONN Health, Farmington, Connecticut, United States of America
- * E-mail:
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13
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Polyomavirus interaction with the DNA damage response. Virol Sin 2015; 30:122-9. [PMID: 25910481 DOI: 10.1007/s12250-015-3583-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 04/15/2015] [Indexed: 12/31/2022] Open
Abstract
Viruses are obligate intracellular parasites that subvert cellular metabolism and pathways to mediate their own replication-normally at the expense of the host cell. Polyomaviruses are a group of small DNA viruses, which have long been studied as a model for eukaryotic DNA replication. Polyomaviruses manipulate host replication proteins, as well as proteins involved in DNA maintenance and repair, to serve as essential cofactors for productive infection. Moreover, evidence suggests that polyomavirus infection poses a unique genotoxic threat to the host cell. In response to any source of DNA damage, cells must initiate an effective DNA damage response (DDR) to maintain genomic integrity, wherein two protein kinases, ataxia telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR), are major regulators of DNA damage recognition and repair. Recent investigation suggests that these essential DDR proteins are required for productive polyomavirus infection. This review will focus on polyomaviruses and their interaction with ATM- and ATR-mediated DNA damage responses and the effect of this interaction on host genomic stability.
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Wendzicki JA, Moore PS, Chang Y. Large T and small T antigens of Merkel cell polyomavirus. Curr Opin Virol 2015; 11:38-43. [PMID: 25681708 DOI: 10.1016/j.coviro.2015.01.009] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 01/19/2015] [Indexed: 12/16/2022]
Abstract
Merkel cell polyomavirus (MCV) is the etiological agent of Merkel cell carcinoma (MCC), a rare and highly lethal human skin cancer. A natural component of skin flora, MCV becomes tumorigenic only after integration into the host DNA together with specific mutations to the viral genome. Research on MCV large T (LT) and small T (sT) antigens, the only viral products expressed in MCC, shows that these major oncoproteins not only possess biochemical functions found in common with other polyomavirus T antigens, but also demonstrate new cellular targets not described in previous polyomavirus models. This review provides a map of the relevant functional motifs and domains in MCV T antigens that have been identified, highlighting their roles in tumorigenesis.
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Affiliation(s)
- Justin A Wendzicki
- Cancer Virology Program, University of Pittsburgh Cancer Institute, Suite 1.8, 5117 Centre Avenue, Pittsburgh, PA 15213, United States
| | - Patrick S Moore
- Cancer Virology Program, University of Pittsburgh Cancer Institute, Suite 1.8, 5117 Centre Avenue, Pittsburgh, PA 15213, United States.
| | - Yuan Chang
- Cancer Virology Program, University of Pittsburgh Cancer Institute, Suite 1.8, 5117 Centre Avenue, Pittsburgh, PA 15213, United States.
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15
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Papillomavirus E7 oncoproteins share functions with polyomavirus small T antigens. J Virol 2014; 89:2857-65. [PMID: 25540383 DOI: 10.1128/jvi.03282-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Many of the small DNA tumor viruses encode transforming proteins that function by targeting critical cellular pathways involved in cell proliferation and survival. In this study, we have examined whether some of the functions of the polyomavirus small T antigens (ST) are shared by the E6 and E7 oncoproteins of two oncogenic papillomaviruses. Using three different assays, we have found that E7 can provide some simian virus 40 (SV40) or murine polyomavirus (PyV) ST functions. Both human papillomavirus 16 (HPV16) and bovine papillomavirus (BPV1) E7 proteins are capable of partially substituting for SV40 ST in a transformation assay that also includes SV40 large T antigen, the catalytic subunit of cellular telomerase, and oncogenic Ras. Like SV40 ST, HPV16 E7 has the ability to override a quiescence block induced by mitogen deprivation. Like PyV ST, it also has the ability to inhibit myoblast differentiation. At least two of these activities are dependent upon the interaction of HPV16 E7 with retinoblastoma protein family members. For small T antigens, interaction with PP2A is needed for each of these functions. Even though there is no strong evidence that E6 or E7 share the ability of small T to interact with PP2A, E7 provides these functions related to cellular transformation. IMPORTANCE DNA tumor viruses have provided major insights into how cancers develop. Some viruses, like the human papillomaviruses, can cause cancer directly. Both the papillomaviruses and the polyomaviruses have served as tools for understanding pathways that are often perturbed in cancer. Here, we have compared the functions of transforming proteins from several DNA tumor viruses, including two papillomaviruses and two polyomaviruses. We tested the papillomavirus E6 and E7 oncoproteins in three functional assays and found that E7 can provide some or all of the functions of the SV40 small T antigen, another well-characterized oncoprotein, in two of these assays. In a third assay, papillomavirus E7 has the same effect as the murine polyomavirus small T protein. In summary, we report several new functions for the papillomavirus E7 proteins, which will contribute new insights into the roles of viruses in cancer and the cellular pathways they perturb in carcinogenesis.
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Verhaegen ME, Mangelberger D, Harms PW, Vozheiko TD, Weick JW, Wilbert DM, Saunders TL, Ermilov AN, Bichakjian CK, Johnson TM, Imperiale MJ, Dlugosz AA. Merkel cell polyomavirus small T antigen is oncogenic in transgenic mice. J Invest Dermatol 2014; 135:1415-1424. [PMID: 25313532 PMCID: PMC4397111 DOI: 10.1038/jid.2014.446] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 09/15/2014] [Accepted: 10/02/2014] [Indexed: 12/17/2022]
Abstract
Merkel cell carcinoma (MCC) is a rare and deadly neuroendocrine skin tumor
frequently associated with clonal integration of a polyomavirus, MCPyV, and MCC tumor
cells express putative polyomavirus oncoproteins small T antigen (sTAg) and truncated
large T antigen (tLTAg). Here, we show robust transforming activity of sTAg in
vivo in a panel of transgenic mouse models. Epithelia of pre-term
sTAg-expressing embryos exhibited hyperplasia, impaired differentiation, increased
proliferation and apoptosis, and activation of a DNA damage response. Epithelial
transformation did not require sTAg interaction with the PP2A protein complex, a tumor
suppressor in some other polyomavirus transformation models, but was strictly dependent on
a recently-described sTAg domain that binds Fbxw7, the substrate-binding component of the
SCF ubiquitin ligase complex. Postnatal induction of sTAg using a Cre-inducible transgene
also led to epithelial transformation with development of lesions resembling squamous cell
carcinoma in situ and elevated expression of Fbxw7 target proteins. Our
data establish that expression of MCPyV sTAg alone is sufficient for rapid neoplastic
transformation in vivo, implicating sTAg as an oncogenic driver in MCC
and perhaps other human malignancies. Moreover, the loss of transforming activity
following mutation of the sTAg Fbxw7 binding domain identifies this domain as crucial for in
vivo transformation.
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Affiliation(s)
| | | | - Paul W Harms
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109.,Department of Pathology, University of Michigan, Ann Arbor, MI 48109
| | - Tracy D Vozheiko
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
| | - Jack W Weick
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
| | - Dawn M Wilbert
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109
| | - Thomas L Saunders
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109
| | | | | | - Timothy M Johnson
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109.,Otolaryngology, University of Michigan, Ann Arbor, MI 48109.,Surgery, University of Michigan, Ann Arbor, MI 48109
| | | | - Andrzej A Dlugosz
- Department of Dermatology, University of Michigan, Ann Arbor, MI 48109.,Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
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Polyomavirus small T antigen interacts with yes-associated protein to regulate cell survival and differentiation. J Virol 2014; 88:12055-64. [PMID: 25122798 DOI: 10.1128/jvi.01399-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Murine polyomavirus small t antigen (PyST) regulates cell cycle, cell survival, apoptosis, and differentiation and cooperates with middle T antigen (MT) to transform primary cells in vitro and in vivo. Like all polyomavirus T antigens, PyST functions largely via its interactions with host cell proteins. Here, we show that PyST binds both Yes-associated protein 1 (YAP1) and YAP2, integral parts of the Hippo signaling pathway, which is a subject of increasing interest in human cancer. The transcription factor TEAD, which is a known target of YAP, is also found in PyST complexes. PyST enhanced YAP association with protein phosphatase 2A (PP2A), leading to decreased YAP phosphorylation. PyST increased YAP levels by decreasing its degradation. This effect was mediated by a reduction in YAP association with β-transducin repeat protein (βTRCP), which is known to regulate YAP turnover in a phosphorylation-dependent manner. Genetic analysis has identified PyST mutants defective in YAP binding. These mutants demonstrated that YAP binding is important for PyST to block myoblast differentiation and to synergize with the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) to promote cell death in 3T3-L1 preadipocytes placed under differentiation conditions. In addition to YAP binding, both of these phenotypes require PyST binding to PP2A. Importance: The Hippo/YAP pathway is a highly conserved cascade important for tissue development and homeostasis. Defects in this pathway are increasingly being associated with cancer. Polyomavirus small t antigen is a viral oncogene that cooperates with middle T antigen in transformation. On its own, small t antigen controls cell survival and differentiation. By binding YAP, small t antigen brings it together with protein phosphatase 2A. This work shows how this association of small t antigen with YAP is important for its effects on cell phenotype. It also suggests that PyST can be used to characterize cellular processes that are regulated by YAP.
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Pores Fernando AT, Andrabi S, Cizmecioglu O, Zhu C, Livingston DM, Higgins JMG, Schaffhausen BS, Roberts TM. Polyoma small T antigen triggers cell death via mitotic catastrophe. Oncogene 2014; 34:2483-92. [PMID: 24998850 PMCID: PMC4286542 DOI: 10.1038/onc.2014.192] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 05/16/2014] [Accepted: 05/28/2014] [Indexed: 12/25/2022]
Abstract
Polyoma small T antigen (PyST), an early gene product of the polyoma virus, has been shown to cause cell death in a number of mammalian cells in a protein phosphatase 2A (PP2A)-dependent manner. In the current study, using a cell line featuring regulated expression of PyST, we found that PyST arrests cells in mitosis. Live-cell and immunofluorescence studies showed that the majority of the PyST expressing cells were arrested in prometaphase with almost no cells progressing beyond metaphase. These cells exhibited defects in chromosomal congression, sister chromatid cohesion and spindle positioning, thereby resulting in the activation of the spindle assembly checkpoint. Prolonged mitotic arrest then led to cell death via mitotic catastrophe. Cell cycle inhibitors that block cells in G1/S prevented PyST-induced death. PyST-induced cell death that occurs during M is not dependent on p53 status. These data suggested, and our results confirmed, that PP2A inhibition could be used to preferentially kill cancer cells with p53 mutations that proliferate normally in the presence of cell cycle inhibitors.
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Affiliation(s)
- A T Pores Fernando
- 1] Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA [2] Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - S Andrabi
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - O Cizmecioglu
- 1] Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA [2] Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - C Zhu
- Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA, USA
| | - D M Livingston
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - J M G Higgins
- 1] Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA, USA [2] Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, UK
| | - B S Schaffhausen
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA, USA
| | - T M Roberts
- 1] Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA [2] Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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Merkel cell polyomavirus small T antigen targets the NEMO adaptor protein to disrupt inflammatory signaling. J Virol 2013; 87:13853-67. [PMID: 24109239 DOI: 10.1128/jvi.02159-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Merkel cell carcinoma (MCC) is a highly aggressive nonmelanoma skin cancer arising from epidermal mechanoreceptor Merkel cells. In 2008, a novel human polyomavirus, Merkel cell polyomavirus (MCPyV), was identified and is strongly implicated in MCC pathogenesis. Currently, little is known regarding the virus-host cell interactions which support virus replication and virus-induced mechanisms in cellular transformation and metastasis. Here we identify a new function of MCPyV small T antigen (ST) as an inhibitor of NF-κB-mediated transcription. This effect is due to an interaction between MCPyV ST and the NF-κB essential modulator (NEMO) adaptor protein. MCPyV ST expression inhibits IκB kinase α (IKKα)/IKKβ-mediated IκB phosphorylation, which limits translocation of the NF-κB heterodimer to the nucleus. Regulation of this process involves a previously undescribed interaction between MCPyV ST and the cellular phosphatase subunits, protein phosphatase 4C (PP4C) and/or protein phosphatase 2A (PP2A) Aβ, but not PP2A Aα. Together, these results highlight a novel function of MCPyV ST to subvert the innate immune response, allowing establishment of early or persistent infection within the host cell.
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Hwang JH, Jiang T, Kulkarni S, Faure N, Schaffhausen BS. Protein phosphatase 2A isoforms utilizing Aβ scaffolds regulate differentiation through control of Akt protein. J Biol Chem 2013; 288:32064-73. [PMID: 24052256 DOI: 10.1074/jbc.m113.497644] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase 2A (PP2A) regulates almost all cell signaling pathways. It consists of a scaffolding A subunit to which a catalytic C subunit and one of many regulatory B subunits bind. Of the more than 80 PP2A isoforms, 10% use Aβ as a scaffold. This study demonstrates the isoform-specific function of the A scaffold subunits. Polyomaviruses have shown the importance of phosphotyrosine, PI3K, and p53 in transformation. Comparisons of polyoma and SV40 small T antigens implicate Aβ in the control of differentiation. Knockdown of Aβ enhanced differentiation. Akt signaling regulated differentiation; its activation or inhibition promoted or blocked it, respectively. Aβ bound Akt. Enhancement of PP2A Aβ/Akt interaction by polyoma small T antigen increased turnover of Akt Ser-473 phosphorylation. Conversely, knockdown of Aβ promoted Akt activity and reduced turnover of phosphate at Ser-473 of Akt. These data provide new insight into the regulation of Akt, a protein of extreme importance in cancer. Furthermore, our results suggest that the role for Aβ in differentiation and perhaps tumor suppression may lie partly in its ability to negatively regulate Akt.
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Affiliation(s)
- Justin H Hwang
- From the Department of Developmental, Molecular & Chemical Biology
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Feltkamp MCW, Kazem S, van der Meijden E, Lauber C, Gorbalenya AE. From Stockholm to Malawi: recent developments in studying human polyomaviruses. J Gen Virol 2013; 94:482-496. [DOI: 10.1099/vir.0.048462-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Until a few years ago the polyomavirus family (Polyomaviridae) included a dozen viruses identified in avian and mammalian hosts. Two of these, the JC and BK-polyomaviruses isolated a long time ago, are known to infect humans and cause severe illness in immunocompromised hosts. Since 2007 an unprecedented number of eight novel polyomaviruses were discovered in humans. Among them are the KI- and WU-polyomaviruses identified in respiratory samples, the Merkel cell polyomavirus found in skin carcinomas and the polyomavirus associated with trichodysplasia spinulosa, a skin disease of transplant patients. Another four novel human polyomaviruses were identified, HPyV6, HPyV7, HPyV9 and the Malawi polyomavirus, so far not associated with any disease. In the same period several novel mammalian polyomaviruses were described. This review summarizes the recent developments in studying the novel human polyomaviruses, and touches upon several aspects of polyomavirus virology, pathogenicity, epidemiology and phylogeny.
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Affiliation(s)
- Mariet C. W. Feltkamp
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Siamaque Kazem
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Els van der Meijden
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Chris Lauber
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Alexander E. Gorbalenya
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119899 Moscow, Russia
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
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