1. |
- Daskalogianni, Chrysoula, et al.
(författare)
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Epstein-Barr virus-encoded EBNA1 and ZEBRA : targets for therapeutic strategies against EBV-carrying cancers
- 2015
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Ingår i: Journal of Pathology. - : Wiley. - 0022-3417 .- 1096-9896. ; 235:2, s. 334-341
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Forskningsöversikt (refereegranskat)abstract
- The EBV-encoded EBNA1 was first discovered 40 years ago, approximately 10 years after the presence of EBV had been demonstrated in Burkitt's lymphoma cells. It took another 10 years before the functions of EBNA1 in maintaining the viral genome were revealed, and it has since been shown to be an essential viral factor expressed in all EBV-carrying cells. Apart from serving to maintain the viral episome and to control viral replication and gene expression, EBNA1 also harbours a cis-acting mechanism that allows virus-carrying host cells to evade the immune system. This relates to a particular glycine-alanine repeat (GAr) within EBNA1 that has the capacity to suppress antigen presentation to the major histocompatibility complex (MHC) class I pathway. We discuss the role of the GAr sequence at the level of mRNA translation initiation, rather than at the protein level, as at least part of the mechanism to avoid MHC presentation. Interfering with this mechanism has become the focus of the development of immune-based therapies against EBV-carrying cancers, and some lead compounds that affect translation of GAr-carrying mRNAs have been identified. In addition, we describe the EBV-encoded ZEBRA factor and the switch from the latent to the lytic cycle as an alternative virus-specific target for treating EBV-carrying cancers. Understanding the molecular mechanisms of how EBNA1 and ZEBRA interfere with cellular pathways not only opens new therapeutic approaches but continues to reveal new cell-biological insights on the interplay between host and virus. This review is a tale of discoveries relating to how EBNA1 and ZEBRA have emerged as targets for specific cancer therapies against EBV-carrying diseases, and serves as an illustration of how mRNA translation can play roles in future immune-based strategies to target viral disease.
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2. |
- Dos Reis, Suzana, et al.
(författare)
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Mode of action of the antiprion drugs 6AP and GA on ribosome assisted protein folding
- 2011
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Ingår i: Biochimie. - : Elsevier BV. - 0300-9084 .- 1638-6183. ; 93:6, s. 1047-1054
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Tidskriftsartikel (refereegranskat)abstract
- The ribosome, the protein synthesis machinery of the cell, has also been implicated in protein folding. This activity resides within the domain V of the main RNA component of the large subunit of the ribosome. It has been shown that two antiprion drugs 6-aminophenanthridine (GAP) and Guanabenz (GA) bind to the ribosomal RNA and inhibit specifically the protein folding activity of the ribosome. Here, we have characterized with biochemical experiments, the mode of inhibition of these two drugs using ribosomes or ribosomal components active in protein folding (referred to as 'ribosomal folding modulators' or RFMs) from both bacteria Escherichia con and yeast Saccharomyces cerevisiae, and human carbonic anhydrase (HCA) as a sample protein. Our results indicate that 6AP and GA inhibit the protein folding activity of the ribosome by competition with the unfolded protein for binding to the ribosome. As a result, the yield of the refolded protein decreases, but the rate of its refolding remains unaffected. Further, 6AP- and GA mediated inhibition of RFM mediated refolding can be reversed by the addition of RFMs in excess. We also demonstrate with delayed addition of the ribosome and the antiprion drugs that there is a short time-span in the range of seconds within which the ribosome interacts with the unfolded protein. Thus we conclude that the protein folding activity of the ribosome is conserved from bacteria to eukaryotes and most likely the substrate for RFMs is an early refolding state of the target protein.
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3. |
- Nguyen, Phu Hai, et al.
(författare)
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Structure-Activity Relationship Study around Guanabenz Identifies Two Derivatives Retaining Antiprion Activity but Having Lost alpha 2-Adrenergic Receptor Agonistic Activity
- 2014
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Ingår i: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 5:10, s. 1075-1082
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Tidskriftsartikel (refereegranskat)abstract
- Guanabenz (GA) is an orally active alpha 2-adrenergic agonist that has been used for many years for the treatment of hypertension. We recently described that GA is also active against both yeast and mammalian prions in an alpha 2-adrenergic receptor-independent manner. These data suggest that this side-activity of GA could be explored for the treatment of prion-based diseases and other amyloid-based disorders. In this perspective, the potent antihypertensive activity of GA happens to be an annoying side-effect that could limit its use. In order to get rid of GA agonist activity at alpha 2-adrenergic receptors, we performed a structure-activity relationship study around GA based on changes of the chlorine positions on the benzene moiety and then on the modifications of the guanidine group. Hence, we identified the two derivatives 6 and 7 that still possess a potent antiprion activity but were totally devoid of any agonist activity at alpha 2-adrenergic receptors. Similarly to GA, 6 and 7 were also able to inhibit the protein folding activity of the ribosome (PFAR) which has been suggested to be involved in prion appearance/maintenance. Therefore, these two GA derivatives are worth being considered as drug candidates.
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4. |
- Oumata, Nassima, et al.
(författare)
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The Toll-Like Receptor Agonist Imiquimod Is Active against Prions
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:8, s. e72112-
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Tidskriftsartikel (refereegranskat)abstract
- Using a yeast-based assay, a previously unsuspected antiprion activity was found for imiquimod (IQ), a potent Toll-like receptor 7 (TLR7) agonist already used for clinical applications. The antiprion activity of IQ was first detected against yeast prions [PSI+] and [URE3], and then against mammalian prion both ex vivo in a cell-based assay and in vivo in a transgenic mouse model for prion diseases. In order to facilitate structure-activity relationship studies, we conducted a new synthetic pathway which provides a more efficient means of producing new IQ chemical derivatives, the activity of which was tested against both yeast and mammalian prions. The comparable antiprion activity of IQ and its chemical derivatives in the above life forms further emphasizes the conservation of prion controlling mechanisms throughout evolution. Interestingly, this study also demonstrated that the antiprion activity of IQ and IQ-derived compounds is independent from their ability to stimulate TLRs. Furthermore, we found that IQ and its active chemical derivatives inhibit the protein folding activity of the ribosome (PFAR) in vitro.
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5. |
- Pang, Yanhong, et al.
(författare)
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The Antiprion Compound 6-Aminophenanthridine Inhibits the Protein Folding Activity of the Ribosome by Direct Competition
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:26, s. 19081-19089
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Tidskriftsartikel (refereegranskat)abstract
- Domain V of the 23S/25S/28S rRNA of the large ribosomal subunit constitutes the active center for the protein folding activity of the ribosome (PFAR). Using in vitro transcribed domain V rRNAs from Escherichia coli and Saccharomyces cerevisiae as the folding modulators and human carbonic anhydrase as a model protein, we demonstrate that PFAR is conserved from prokaryotes to eukaryotes. It was shown previously that 6-aminophenanthridine (6AP), an antiprion compound, inhibits PFAR. Here, using UV cross-linking followed by primer extension, we show that the protein substrates and 6AP interact with a common set of nucleotides on domain V of 23S rRNA. Mutations at the interaction sites decreased PFAR and resulted in loss or change of the binding pattern for both the protein substrates and 6AP. Moreover, kinetic analysis of human carbonic anhydrase refolding showed that 6AP decreased the yield of the refolded protein but did not affect the rate of refolding. Thus, we conclude that 6AP competitively occludes the protein substrates from binding to rRNA and thereby inhibits PFAR. Finally, we propose a scheme clarifying the mechanism by which 6AP inhibits PFAR.
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6. |
- Tribouillard-Tanvier, Deborah, et al.
(författare)
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Protein Folding Activity of Ribosomal RNA Is a Selective Target of Two Unrelated Antiprion Drugs
- 2008
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 3:5, s. e2174-
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Tidskriftsartikel (refereegranskat)abstract
- Background: 6-Aminophenanthridine (6AP) and Guanabenz (GA, a drug currently in use for the treatment of hypertension) were isolated as antiprion drugs using a yeast-based assay. These structurally unrelated molecules are also active against mammalian prion in several cell-based assays and in vivo in a mouse model for prion-based diseases. Methodology/Principal Findings: Here we report the identification of cellular targets of these drugs. Using affinity chromatography matrices for both drugs, we demonstrate an RNA-dependent interaction of 6AP and GA with the ribosome. These specific interactions have no effect on the peptidyl transferase activity of the ribosome or on global translation. In contrast, 6AP and GA specifically inhibit the ribosomal RNA-mediated protein folding activity of the ribosome. Conclusion/Significance: 6AP and GA are therefore the first compounds to selectively inhibit the protein folding activity of the ribosome. They thus constitute precious tools to study the yet largely unexplored biological role of this protein folding activity.
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