The Experts below are selected from a list of 14538 Experts worldwide ranked by ideXlab platform
Thomas Dobner - One of the best experts on this subject based on the ideXlab platform.
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differential regulation of cellular fam111b by human adenovirus c type 5 e1 oncogenes
Viruses, 2021Co-Authors: Britta Wilkens, Anastasia Solomatina, Judith Martin, Michael Melling, Paloma Hidalgo, Luca D Bertzbach, Thomas Speiseder, Thomas DobnerAbstract:The adenovirus type 5 (HAdV-C5) E1 transcription unit encodes regulatory proteins that are essential for Viral replication and Transformation. Among these, E1A and E1B-55K act as key multifunctional HAdV-C5 proteins involved in various steps of the Viral replication cycle and in virus-induced cell Transformation. In this context, HAdV-C5-mediated dysregulations of cellular factors such as the tumor suppressors p53 and pRB have been intensively investigated. However, cellular components of downstream events that could affect infection and Viral Transformation are widely unknown. We recently observed that cellular FAM111B is highly regulated in an E1A-dependent fashion. Intriguingly, previous reports suggest that FAM111B might play roles in tumorigenesis, but its exact functions are not known to date. Here, we set out to investigate the role of FAM111B in HAdV-C5 infections. We found that (i) FAM111B levels are upregulated early and downregulated late during infection, that (ii) FAM111B expression is differentially regulated, that (iii) FAM111B expression levels depend on the presence of E1B-55K and E4orf6 and that (iv) a FAM111B knockdown increases HAdV-C5 replication. Our data indicate that FAM111B acts as an anti-adenoViral host factor that is involved in host cell defense mechanisms in productive HAdV-C5 infection. Moreover, these findings suggest that FAM111B might play an important role in the host antiViral immune response that is counteracted by HAdV-C5 E1B-55K and E4orf6 oncoproteins.
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efficient Transformation of primary human mesenchymal stromal cells by adenovirus early region 1 oncogenes
Journal of Virology, 2017Co-Authors: Thomas Speiseder, Helga Hofmannsieber, Estefania Rodriguez, Anna Schellenberg, Nuray Akyuz, Judith Dierlamm, Thilo Spruss, Claudia Lange, Thomas DobnerAbstract:Previous observations that human amniotic fluid cells (AFC) can be transformed by human adenovirus type 5 (HAdV-5) E1A/E1B oncogenes prompted us to identify the target cells in the AFC population that are susceptible to Transformation. Our results demonstrate that one cell type corresponding to mesenchymal stem/stroma cells (hMSCs) can be reproducibly transformed by HAdV-5 E1A/E1B oncogenes as efficiently as primary rodent cultures. HAdV-5 E1-transformed hMSCs exhibit all properties commonly associated with a high grade of oncogenic Transformation, including enhanced cell proliferation, anchorage-independent growth, increased growth rate, and high telomerase activity as well as numerical and structural chromosomal aberrations. These data confirm previous work showing that HAdV preferentially transforms cells of mesenchymal origin in rodents. More importantly, they demonstrate for the first time that human cells with stem cell characteristics can be completely transformed by HAdV oncogenes in tissue culture with high efficiency. Our findings strongly support the hypothesis that undifferentiated progenitor cells or cells with stem cell-like properties are highly susceptible targets for HAdV-mediated cell Transformation and suggest that virus-associated tumors in humans may originate, at least in part, from infections of these cell types. We expect that primary hMSCs will replace the primary rodent cultures in HAdV Viral Transformation studies and are confident that these investigations will continue to uncover general principles of Viral oncogenesis that can be extended to human DNA tumor viruses as well. IMPORTANCE It is generally believed that Transformation of primary human cells with HAdV-5 E1 oncogenes is very inefficient. However, a few cell lines have been successfully transformed with HAdV-5 E1A and E1B, indicating that there is a certain cell type which is susceptible to HAdV-mediated Transformation. Interestingly, all those cell lines have been derived from human embryonic tissue, albeit the exact cell type is not known yet. We show for the first time the successful Transformation of primary human mesenchymal stromal cells (hMSCs) by HAdV-5 E1A and E1B. Further, we show upon HAdV-5 E1A and E1B expression that these primary progenitor cells exhibit features of tumor cells and can no longer be differentiated into the adipogenic, chondrogenic, or osteogenic lineage. Hence, primary hMSCs represent a robust and novel model system to elucidate the underlying molecular mechanisms of adenovirus-mediated Transformation of multipotent human progenitor cells.
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spoc1 mediated antiViral host cell response is antagonized early in human adenovirus type 5 infection
PLOS Pathogens, 2013Co-Authors: Sabrina Schreiner, Sarah Kinkley, Carolin Burck, Andreas Mund, Peter Wimmer, Tobias Schubert, Peter Groitl, Hans Will, Thomas DobnerAbstract:Little is known about immediate phases after Viral infection and how an incoming Viral genome complex counteracts host cell defenses, before the start of Viral gene expression. Adenovirus (Ad) serves as an ideal model, since entry and onset of gene expression are rapid and highly efficient, and mechanisms used 24–48 hours post infection to counteract host antiViral and DNA repair factors (e.g. p53, Mre11, Daxx) are well studied. Here, we identify an even earlier host cell target for Ad, the chromatin-associated factor and epigenetic reader, SPOC1, recently found recruited to double strand breaks, and playing a role in DNA damage response. SPOC1 co-localized with Viral replication centers in the host cell nucleus, interacted with Ad DNA, and repressed Viral gene expression at the transcriptional level. We discovered that this SPOC1-mediated restriction imposed upon Ad growth is relieved by its functional association with the Ad major core protein pVII that enters with the Viral genome, followed by E1B-55K/E4orf6-dependent proteasomal degradation of SPOC1. Mimicking removal of SPOC1 in the cell, knock down of this cellular restriction factor using RNAi techniques resulted in significantly increased Ad replication, including enhanced Viral gene expression. However, depletion of SPOC1 also reduced the efficiency of E1B-55K transcriptional repression of cellular promoters, with possible implications for Viral Transformation. Intriguingly, not exclusive to Ad infection, other human pathogenic viruses (HSV-1, HSV-2, HIV-1, and HCV) also depleted SPOC1 in infected cells. Our findings provide a general model for how pathogenic human viruses antagonize intrinsic SPOC1-mediated antiViral responses in their host cells. A better understanding of Viral entry and early restrictive functions in host cells should provide new perspectives for developing antiViral agents and therapies. Conversely, for Ad vectors used in gene therapy, counteracting mechanisms eradicating incoming Viral DNA would increase Ad vector efficacy and safety for the patient.
Brian Schaffhausen - One of the best experts on this subject based on the ideXlab platform.
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Cellular Transformation by Simian Virus 40 and Murine Polyoma Virus T antigens
Seminars in cancer biology, 2009Co-Authors: Jingwei Cheng, James A Decaprio, Michele M. Fluck, Brian SchaffhausenAbstract:Simian Virus 40 (SV40) and Mouse Polyoma Virus (PY) are small DNA tumor viruses that have been used extensively to study cellular Transformation. The SV40 early region encodes three tumor antigens, large T (LT), small T (ST) and 17KT that contribute to cellular Transformation. While PY also encodes LT and ST, the unique middle T (MT) generates most of the transforming activity. SV40 LT mediated Transformation requires binding to the tumor suppressor proteins Rb and p53 in the nucleus and ST binding to the protein phosphatase PP2A in the cytoplasm. SV40 LT also binds to several additional cellular proteins including p300, CBP, Cul7, IRS1, Bub1, Nbs1 and Fbxw7 that contribute to Viral Transformation. PY MT Transformation is dependent on binding to PP2A and the Src family protein tyrosine kinases (PTK) and assembly of a signaling complex on cell membranes that leads to Transformation in a manner similar to Her2/neu. Phosphorylation of MT tyrosine residues activates key signaling molecules including Shc/Grb2, PI3K and PLCgamma1. The unique contributions of SV40 LT and ST and PY MT to cellular Transformation have provided significant insights into our understanding of tumor suppressors, oncogenes and the process of oncogenesis.
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Lessons from Polyoma Middle T Antigen on Signaling and Transformation: A DNA Tumor Virus Contribution to the War on Cancer
Virology, 2008Co-Authors: Brian Schaffhausen, Thomas M. RobertsAbstract:Abstract Middle T antigen (MT) is the principal oncogene of murine polyomavirus. Its study has led to the discovery of the roles of tyrosine kinase and phosphoinositide 3-kinase (PI3K) signaling in mammalian growth control and Transformation. MT is necessary for Viral Transformation in tissue culture cells and tumorigenesis in animals. When expressed alone as a transgene, MT causes tumors in a wide variety of tissues. It has no known catalytic activity, but rather acts by assembling cellular signal transduction molecules. Protein phosphatase 2A, protein tyrosine kinases of the src family, PI3K, phospholipase Cγ1 as well as the Shc/Grb2 adaptors are all assembled on MT. Their activation sets off a series of signaling cascades. Analyses of virus mutants as well as transgenic animals have demonstrated that the effects of a given signal depend not only tissue type, but on the genetic background of the host animal. There remain many opportunities as we seek a full molecular understanding of MT and apply some of its lessons to human cancer.
James A Decaprio - One of the best experts on this subject based on the ideXlab platform.
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Cellular Transformation by Simian Virus 40 and Murine Polyoma Virus T antigens
Seminars in cancer biology, 2009Co-Authors: Jingwei Cheng, James A Decaprio, Michele M. Fluck, Brian SchaffhausenAbstract:Simian Virus 40 (SV40) and Mouse Polyoma Virus (PY) are small DNA tumor viruses that have been used extensively to study cellular Transformation. The SV40 early region encodes three tumor antigens, large T (LT), small T (ST) and 17KT that contribute to cellular Transformation. While PY also encodes LT and ST, the unique middle T (MT) generates most of the transforming activity. SV40 LT mediated Transformation requires binding to the tumor suppressor proteins Rb and p53 in the nucleus and ST binding to the protein phosphatase PP2A in the cytoplasm. SV40 LT also binds to several additional cellular proteins including p300, CBP, Cul7, IRS1, Bub1, Nbs1 and Fbxw7 that contribute to Viral Transformation. PY MT Transformation is dependent on binding to PP2A and the Src family protein tyrosine kinases (PTK) and assembly of a signaling complex on cell membranes that leads to Transformation in a manner similar to Her2/neu. Phosphorylation of MT tyrosine residues activates key signaling molecules including Shc/Grb2, PI3K and PLCgamma1. The unique contributions of SV40 LT and ST and PY MT to cellular Transformation have provided significant insights into our understanding of tumor suppressors, oncogenes and the process of oncogenesis.
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how the rb tumor suppressor structure and function was revealed by the study of adenovirus and sv40
Virology, 2009Co-Authors: James A DecaprioAbstract:The review recounts the history of how the study of the DNA tumor viruses including polyoma, SV40 and Adenovirus brought key insights into the structure and function of the Retinoblastoma protein (Rb). Knudsen's model of the two-hit hypothesis to explain patterns of hereditary and sporadic retinoblastoma provided the foundation for the tumor suppressor hypothesis that ultimately led to the cloning of the Rb gene. The discovery that SV40 and Adenovirus could cause tumors when inoculated into animals was startling not only because SV40 had contaminated the poliovirus vaccine and Adenovirus was a common cause of Viral induced pneumonia but also because they provided an opportunity to study the genetics and biochemistry of cancer. Studies of mutant forms of these viruses led to the identification of the E1A and Large T antigen (LT) oncogenes and their small transforming elements including the Adenovirus Conserved Regions (CR), the SV40 J domain and the LxCxE motif. The immunoprecipitation studies that initially revealed the size and ultimately the identity of cellular proteins that could bind to these transforming elements were enabled by the widespread development of highly specific monoclonal antibodies against E1A and LT. The identification of Rb as an E1A and LT interacting protein quickly led to the cloning of p107, p130, p300, CBP, p400 and TRRAP and the concept that Viral Transformation was due, at least in part, to the perturbation of the function of normal cellular proteins. In addition, studies on the ability of E1A to transactivate the Adenovirus E2 promoter led to the cloning of the heterodimeric E2F and DP transcription factor and recognition that Rb repressed transcription of cellular genes required for cell cycle entry and progression. More recent studies have revealed how E1A and LT combine the activity of Rb and the other cellular associated proteins to perturb expression of many genes during Viral infection and tumor formation.
Charles N Cole - One of the best experts on this subject based on the ideXlab platform.
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Transformation of a continuous rat embryo fibroblast cell line requires three separate domains of simian virus 40 large t antigen
Journal of Virology, 1992Co-Authors: Jiyue Y Zhu, P W Rice, L Gorsch, M Abate, Charles N ColeAbstract:Mouse C3H 10T1/2 cells and the established rat embryo fibroblast cell line REF-52 are two cell lines widely used in studies of Viral Transformation. Studies have shown that Transformation of 10T1/2 cells requires only the amino-terminal 121 amino acids of simian virus 40 (SV40) large T antigen, while Transformation of REF-52 cells requires considerably more of large T antigen, extending from near the N terminus to beyond residue 600. The ability of a large set of linker insertion, small deletion, and point mutants of SV40 T antigen to transform these two cell lines and to bind p105Rb was determined. Transformation of 10T1/2 cells was greatly reduced by mutations within the first exon of the gene for large T antigen but was only modestly affected by mutations affecting the p105Rb binding site or the p53 binding region. All mutants defective for Transformation of 10T1/2 cells were also defective for Transformation of REF-52 cells. In addition, mutants whose T antigens had alterations in the Rb binding site showed a substantial reduction in Transformation of REF-52 cells, and the degree of this reduction could be correlated with the ability of the mutant T antigens to bind p105Rb. There was a tight correlation between the ability of mutants to transform REF-52 cells and the ability of their T antigens to bind p53. These results demonstrate that multiple regions of large T antigen are required for full Transformation by SV40.
Thomas Speiseder - One of the best experts on this subject based on the ideXlab platform.
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differential regulation of cellular fam111b by human adenovirus c type 5 e1 oncogenes
Viruses, 2021Co-Authors: Britta Wilkens, Anastasia Solomatina, Judith Martin, Michael Melling, Paloma Hidalgo, Luca D Bertzbach, Thomas Speiseder, Thomas DobnerAbstract:The adenovirus type 5 (HAdV-C5) E1 transcription unit encodes regulatory proteins that are essential for Viral replication and Transformation. Among these, E1A and E1B-55K act as key multifunctional HAdV-C5 proteins involved in various steps of the Viral replication cycle and in virus-induced cell Transformation. In this context, HAdV-C5-mediated dysregulations of cellular factors such as the tumor suppressors p53 and pRB have been intensively investigated. However, cellular components of downstream events that could affect infection and Viral Transformation are widely unknown. We recently observed that cellular FAM111B is highly regulated in an E1A-dependent fashion. Intriguingly, previous reports suggest that FAM111B might play roles in tumorigenesis, but its exact functions are not known to date. Here, we set out to investigate the role of FAM111B in HAdV-C5 infections. We found that (i) FAM111B levels are upregulated early and downregulated late during infection, that (ii) FAM111B expression is differentially regulated, that (iii) FAM111B expression levels depend on the presence of E1B-55K and E4orf6 and that (iv) a FAM111B knockdown increases HAdV-C5 replication. Our data indicate that FAM111B acts as an anti-adenoViral host factor that is involved in host cell defense mechanisms in productive HAdV-C5 infection. Moreover, these findings suggest that FAM111B might play an important role in the host antiViral immune response that is counteracted by HAdV-C5 E1B-55K and E4orf6 oncoproteins.
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efficient Transformation of primary human mesenchymal stromal cells by adenovirus early region 1 oncogenes
Journal of Virology, 2017Co-Authors: Thomas Speiseder, Helga Hofmannsieber, Estefania Rodriguez, Anna Schellenberg, Nuray Akyuz, Judith Dierlamm, Thilo Spruss, Claudia Lange, Thomas DobnerAbstract:Previous observations that human amniotic fluid cells (AFC) can be transformed by human adenovirus type 5 (HAdV-5) E1A/E1B oncogenes prompted us to identify the target cells in the AFC population that are susceptible to Transformation. Our results demonstrate that one cell type corresponding to mesenchymal stem/stroma cells (hMSCs) can be reproducibly transformed by HAdV-5 E1A/E1B oncogenes as efficiently as primary rodent cultures. HAdV-5 E1-transformed hMSCs exhibit all properties commonly associated with a high grade of oncogenic Transformation, including enhanced cell proliferation, anchorage-independent growth, increased growth rate, and high telomerase activity as well as numerical and structural chromosomal aberrations. These data confirm previous work showing that HAdV preferentially transforms cells of mesenchymal origin in rodents. More importantly, they demonstrate for the first time that human cells with stem cell characteristics can be completely transformed by HAdV oncogenes in tissue culture with high efficiency. Our findings strongly support the hypothesis that undifferentiated progenitor cells or cells with stem cell-like properties are highly susceptible targets for HAdV-mediated cell Transformation and suggest that virus-associated tumors in humans may originate, at least in part, from infections of these cell types. We expect that primary hMSCs will replace the primary rodent cultures in HAdV Viral Transformation studies and are confident that these investigations will continue to uncover general principles of Viral oncogenesis that can be extended to human DNA tumor viruses as well. IMPORTANCE It is generally believed that Transformation of primary human cells with HAdV-5 E1 oncogenes is very inefficient. However, a few cell lines have been successfully transformed with HAdV-5 E1A and E1B, indicating that there is a certain cell type which is susceptible to HAdV-mediated Transformation. Interestingly, all those cell lines have been derived from human embryonic tissue, albeit the exact cell type is not known yet. We show for the first time the successful Transformation of primary human mesenchymal stromal cells (hMSCs) by HAdV-5 E1A and E1B. Further, we show upon HAdV-5 E1A and E1B expression that these primary progenitor cells exhibit features of tumor cells and can no longer be differentiated into the adipogenic, chondrogenic, or osteogenic lineage. Hence, primary hMSCs represent a robust and novel model system to elucidate the underlying molecular mechanisms of adenovirus-mediated Transformation of multipotent human progenitor cells.
