| 1. |
- Darekar, Suhas
(författare)
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The role of EBNA binding proteins in cell transformation
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epstein-Barr virus (EBV) infects majority of the human population and maintains sub-clinical infection. However, under certain conditions it is associated with several B-cell malignancies, such as Burkitt lymphoma, Hodgkin’s lymphoma etc. Moreover, EBV also plays a causative role in acquired immunodeficiency syndrome (AIDS) associated lymphomas and post-transplant lymphoproliferative disease (PTLD). EBV maintains latent infection and expresses a particular set of proteins that are necessary for host cell proliferation. Studying function of EBV latent proteins could help us to understand the mechanisms underlying EBV induced B-cell transformation. EBV transformed B cells, i.e. lymphoblastoid cell lines (LCLs) is a well- established in vitro model system to study the molecular mechanisms of B-cell transformation. In the present work, we have identified vitamin D receptor (VDR) as a binding partner of EBNA3. We showed that EBNA3 can block the VDR mediated gene transactivation and protects B-cells from vitamin D3 induced growth arrest/ apoptosis. We have observed that hypoxia inducible factor 1 alpha (HIF1α) is stabilized in LCLs at normoxic conditions. HIF1α is not hydroxylated and therefore it is not degraded in LCLs. We have shown that prolylhydroxylases 1 and 2 (PHD1 and 2) that are responsible for hydroxylation of HIF1α, form complexes with EBNA5 and EBNA3, respectively. Due to this binding catalytic activity of PHDs is blocked, resulting in inhibition of HIF1α hydroxylation and subsequent degradation. Stabilized HIF1α is transcriptionally active and induces genes that are involved in glycolysis. Moreover, LCLs have high levels of pyruvate and lactate in contrast to mitogen activated B cells, indicating induction of aerobic glycolysis or Warburg effect. We have shown that mitochondrial ribosomal protein MRPS18-2 (S18-2), an EBNA6 binding protein, can immortalize rat embryonic fibroblasts (REFs). These immortalized cells express stem cell markers like SSEA1, Sox2, Oct3/4 and have the characteristics of embryonic stem cells. S18-2 also immortalized the adult rat skin fibroblasts (RSFs). Moreover, single clones from immortalized REFs and RSFs resulted in tumors in SCID mice. This thesis work reveals three different aspects of EBV induced B-cell transformation, i.e. protection from vitamin D3 induced apoptosis, metabolic adaptation required for proliferation and hijacking functions of novel protein MRPS18-2 for immortalization.
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| 2. |
- Ladds, Marcus J. G. W., et al.
(författare)
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A DHODH inhibitor increases p53 synthesis and enhances tumor cell killing by p53 degradation blockage
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The development of non-genotoxic therapies that activate wild-type p53 in tumors is of great interest since the discovery of p53 as a tumor suppressor. Here we report the identification of over 100 small-molecules activating p53 in cells. We elucidate the mechanism of action of a chiral tetrahydroindazole (HZ00), and through target deconvolution, we deduce that its active enantiomer (R)-HZ00, inhibits dihydroorotate dehydrogenase (DHODH). The chiral specificity of HZ05, a more potent analog, is revealed by the crystal structure of the (R)-HZ05/DHODH complex. Twelve other DHODH inhibitor chemotypes are detailed among the p53 activators, which identifies DHODH as a frequent target for structurally diverse compounds. We observe that HZ compounds accumulate cancer cells in S-phase, increase p53 synthesis, and synergize with an inhibitor of p53 degradation to reduce tumor growth in vivo. We, therefore, propose a strategy to promote cancer cell killing by p53 instead of its reversible cell cycle arresting effect.
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| 3. |
- Yenamandra, Surya Pavan, et al.
(författare)
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Epstein-Barr virus encoded EBNA-3 binds to vitamin D receptor and blocks activation of its target genes
- 2010
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Ingår i: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 67:24, s. 4249-4256
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Tidskriftsartikel (refereegranskat)abstract
- Epstein-Barr virus (EBV) is a human gamma herpes virus that infects B cells and induces their transformation into immortalized lymphoblasts that can grow as cell lines (LCLs) in vitro. EBNA-3 is a member of the EBNA-3-protein family that can regulate transcription of cellular and viral genes. The identification of EBNA-3 cellular partners and a study of its influence on cellular pathways are important for understanding the transforming action of the virus. In this work, we have identified the vitamin D receptor (VDR) protein as a binding partner of EBNA-3. We found that EBNA3 blocks the activation of VDR-dependent genes and protects LCLs against vitamin-D3-induced growth arrest and/or apoptosis. The presented data shed some light on the anti-apoptotic EBV program and the role of the EBNA-3-VDR interaction in the viral strategy.
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