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- Coppotelli, Giuseppe, et al.
(författare)
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The Epstein-Barr virus nuclear antigen-1 reprograms transcription by mimicry of high mobility group A proteins
- 2013
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 41:5, s. 2950-2962
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Tidskriftsartikel (refereegranskat)abstract
- Viral proteins reprogram their host cells by hijacking regulatory components of protein networks. Here we describe a novel property of the Epstein-Barr virus (EBV) nuclear antigen-1 (EBNA1) that may underlie the capacity of the virus to promote a global remodeling of chromatin architecture and cellular transcription. We found that the expression of EBNA1 in transfected human and mouse cells is associated with decreased prevalence of heterochromatin foci, enhanced accessibility of cellular DNA to micrococcal nuclease digestion and decreased average length of nucleosome repeats, suggesting de-protection of the nucleosome linker regions. This is a direct effect of EBNA1 because targeting the viral protein to heterochromatin promotes large-scale chromatin decondensation with slow kinetics and independent of the recruitment of adenosine triphosphate-dependent chromatin remodelers. The remodeling function is mediated by a bipartite Gly-Arg rich domain of EBNA1 that resembles the AT-hook of High Mobility Group A (HMGA) architectural transcription factors. Similar to HMGAs, EBNA1 is highly mobile in interphase nuclei and promotes the mobility of linker histone H1, which counteracts chromatin condensation and alters the transcription of numerous cellular genes. Thus, by regulating chromatin compaction, EBNA1 may reset cellular transcription during infection and prime the infected cells for malignant transformation.
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| 2. |
- Guerra, Lina, et al.
(författare)
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Bacterial genotoxin triggers FEN1-dependent RhoA activation, cytoskeleton remodeling and cell survival
- 2011
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Ingår i: Journal of Cell Science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 124:16, s. 2735-2742
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Tidskriftsartikel (refereegranskat)abstract
- The DNA damage response triggered by bacterial cytolethal distending toxins (CDTs) is associated with activation of the actin-regulating protein RhoA and phosphorylation of the downstream-regulated mitogen-activated protein kinase (MAPK) p38, which promotes the survival of intoxicated (i.e. cells exposed to a bacterial toxin) cells. To identify the effectors of this CDT-induced survival response, we screened a library of 4492 Saccharomyces cerevisiae mutants that carry deletions in nonessential genes for reduced growth following inducible expression of CdtB. We identified 78 genes whose deletion confers hypersensitivity to toxin. Bioinformatics analysis revealed that DNA repair and endocytosis were the two most overrepresented signaling pathways. Among the human orthologs present in our data set, FEN1 and TSG101 regulate DNA repair and endocytosis, respectively, and also share common interacting partners with RhoA. We further demonstrate that FEN1, but not TSG101, regulates cell survival, MAPK p38 phosphorylation, RhoA activation and actin cytoskeleton reorganization in response to DNA damage. Our data reveal a previously unrecognized crosstalk between DNA damage and cytoskeleton dynamics in the regulation of cell survival, and might provide new insights on the role of chronic bacteria infection in carcinogenesis.
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| 3. |
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| 4. |
- Sompallae, Ramakrishna Rao
(författare)
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In silico analysis of pathways targeted by EBV infection and malignant transformation
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epstein-Barr virus (EBV) is a ubiquitous γ-herpes virus with dual cell tropism for human B-lymphocytes and epithelial cells. EBV infection is linked to several malignancies such as Burkitt s lymphoma (BL) and nasopharyngeal carcinoma (NPC). In vitro EBV is a potent transforming virus that converts resting B-lymphocytes into indefinitely proliferating lymphoblastoid cells (LCLs). The overall aim of this study was to develop and utilize bioinformatics methods to dissect the molecular mechanisms by which EBV modulates the cellular environment. EBV is a large DNA virus that encodes about 100 open reading frames (ORFs) expressed at various times during infection. Using established sequence search methods such as patterns and hidden Markov models (HMM), we have identified catalytic domains of ubiquitin specific proteases (deubiquitinating enzymes, DUBs) in a limited number of EBV ORFs. The DUB activity of three high scoring candidates: BPLF1, BSLF1 and BXLF1, was confirmed by functional and mutational analysis (Paper-I). EBV establishes distinct programs of viral gene expression in latently infected and malignant cells. The EBV nuclear antigen (EBNA)-1 is expressed in all EBV carrying proliferating cells. EBNA-1 has been associated with the induction of cellular oxidative stress due to the production of reactive oxygen species (ROS) and DNA damage. To search for the cellular genes involved in these effects we used gene expression data sets from public databases. By analyzing the expression of genes involved in ROS metabolism in EBV positive and negative Burkitt's lymphoma (BL) cell lines and lymphoblastoid cell lines (LCL) we found that the NADPH oxidase (NOX)-2 is induced in cells expressing EBNA-1. Activation of the NOX2 gene by EBNA-1 is associated with the induction and/or maintenance of genomic instability, a critical step in malignant transformation (Paper-II). The expression of EBNA-1 is associated with a global rearrangement of cellular transcription. To investigate the primary and secondary targets of this transcriptional effect we have analyzed the gene expression profiles of stable and inducible EBNA-1 expressing cells. Functional analysis of the regulated transcripts revealed that EBNA-1 influences the expression of genes involved in the maintenance of chromatin architecture. Several subunits of chromatin remodeling complexes were down-regulated on EBNA-1 expression (Paper-III). Microarray analysis and systems biology approaches were implemented to investigate the cellular pathways modulated by tripeptidyl peptidase II (TPPII) a cellular protein that is highly expressed in BL cells and participates in the induction of the malignant phenotype. Comparison of the gene expression profiles of control and TPPII knockdown BL cells and systems level analysis of differentially regulated genes demonstrated that the MAPK signaling pathway is selectively inactivated by TPPII knockdown (Paper-IV). In summary, this work demonstrated the potential of bioinformatics tools and highthroughput genomic approaches in identifying the novel strategies of EBV.
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