The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Penelope Mavromara - One of the best experts on this subject based on the ideXlab platform.
-
hepatitis c virus core 1 ARF Protein modulates the cyclin d1 prb pathway and promotes carcinogenesis
Journal of Virology, 2018Co-Authors: Savvina Moustafa, Ioannis Karakasiliotis, Penelope MavromaraAbstract:Viruses often encompass overlapping reading frames and unconventional translation mechanisms in order to maximize the output from a minimum genome and to orchestrate their timely gene expression. Hepatitis C virus (HCV) possesses such an unconventional open reading frame (ORF) within the core-coding region, encoding an additional Protein, initially designated ARFP, F, or core+1. Two predominant isoforms of core+1/ARFP have been reported, core+1/L, initiating from codon 26, and core+1/S, initiating from codons 85/87 of the polyProtein coding region. The biological significance of core+1/ARFP expression remains elusive. The aim of the present study was to gain insight into the functional and pathological properties of core+1/ARFP through its interaction with the host cell, combining in vitro and in vivo approaches. Our data provide strong evidence that the core+1/ARFP of HCV-1a stimulates cell proliferation in Huh7-based cell lines expressing either core+1/S or core+1/L isoforms and in transgenic liver disease mouse models expressing core+1/S Protein in a liver-specific manner. Both isoforms of core+1/ARFP increase the levels of cyclin D1 and phosphorylated Rb, thus promoting the cell cycle. In addition, core+1/S was found to enhance liver regeneration and oncogenesis in transgenic mice. The induction of the cell cycle together with increased mRNA levels of cell proliferation-related oncogenes in cells expressing the core+1/ARFP Proteins argue for an oncogenic potential of these Proteins and an important role in HCV-associated pathogenesis.IMPORTANCE This study sheds light on the biological importance of a unique HCV Protein. We show here that core+1/ARFP of HCV-1a interacts with the host machinery, leading to acceleration of the cell cycle and enhancement of liver carcinogenesis. This pathological mechanism(s) may complement the action of other viral Proteins with oncogenic properties, leading to the development of hepatocellular carcinoma. In addition, given that immunological responses to core+1/ARFP have been correlated with liver disease severity in chronic HCV patients, we expect that the present work will assist in clarifying the pathophysiological relevance of this Protein as a biomarker of disease progression.
-
High prevalence of antibodies to core+1/ARF Protein in HCV-infected patients with advanced cirrhosis.
The Journal of general virology, 2017Co-Authors: Katerina Kassela, Ioannis Karakasiliotis, Stefanos Charpantidis, John Koskinas, Theodora Mylopoulou, Konstantinos Mimidis, Christoph Sarrazin, Georgios Grammatikos, Penelope MavromaraAbstract:Hepatitis C virus (HCV) possesses a second open reading frame (ORF) within the core gene encoding an additional Protein, known as the alternative reading frame Protein (ARFP), F or core+1. The biological significance of the core+1/ARF Protein remains elusive. However, several independent studies have shown the presence of core+1/ARFP antibodies in chronically HCV-infected patients. Furthermore, a higher prevalence of core+1/ARFP antibodies was detected in patients with HCV-associated hepatocellular carcinoma (HCC). Here, we investigated the incidence of core+1/ARFPantibodies in chronically HCV-infected patients at different stages of cirrhosis in comparison to chronically HCV-infected patients at earlier stages of disease. Using ELISA, we assessed the prevalence of anti-core+1 antibodies in 30 patients with advanced cirrhosis [model for end-stage liver disease (MELD) ≥15] in comparison with 50 patients with mild cirrhosis (MELD
-
expression of the novel hepatitis c virus core 1 ARF Protein in the context of jfh1 based replicons
Journal of Virology, 2015Co-Authors: Ioly Kottaloizou, Ioannis Karakasiliotis, Niki Vassilaki, Panagiotis Sakellariou, Ralf Bartenschlager, Penelope MavromaraAbstract:Hepatitis C virus contains a second open reading frame within the core gene, designated core+1/ARF. Here we demonstrate for the first time expression of core+1/ARF Protein in the context of a bicistronic JFH1-based replicon and report the production of two isoforms, core+1/L (long) and core+1/S (short), with different kinetics.
-
Expression of the Novel Hepatitis C Virus Core+1/ARF Protein in the Context of JFH1-Based Replicons
Journal of virology, 2015Co-Authors: Ioly Kotta-loizou, Ioannis Karakasiliotis, Niki Vassilaki, Panagiotis Sakellariou, Ralf Bartenschlager, Penelope MavromaraAbstract:Hepatitis C virus contains a second open reading frame within the core gene, designated core+1/ARF. Here we demonstrate for the first time expression of core+1/ARF Protein in the context of a bicistronic JFH1-based replicon and report the production of two isoforms, core+1/L (long) and core+1/S (short), with different kinetics.
-
hepatitis c virus core 1 ARF Protein decreases hepcidin transcription through an ap1 binding site
Journal of General Virology, 2013Co-Authors: Ioly Kottaloizou, Niki Vassilaki, Ralf Bartenschlager, George Pissas, Athanassios Kakkanas, Latifa Bakiri, Penelope MavromaraAbstract:Chronic viral hepatitis C is characterized by iron accumulation in the liver, and hepcidin regulates iron absorption. Hepatitis C virus (HCV) core+1/ARFP is a novel Protein produced by a second functional ORF within the core gene. Here, using reporter assays and HCV bicistronic replicons, we show that, similarly to core, core+1/ARFP decreases hepcidin expression in hepatoma cells. The activator Protein 1 (AP1) binding site of the human hepcidin promoter, shown here to be relevant to basal promoter activity and to the repression by core, is essential for the downregulation by core+1/ARFP while the previously described C/EBP (CCAAT/enhancer binding Protein) and STAT (signal transducer and activator of transcription) sites are not. Consistently, expression of the AP1 components c-jun and c-fos obliterated the repressive effect of core and core+1/ARFP. In conclusion, we provide evidence that core+1/ARFP downregulates AP1-mediated transcription, providing new insights into the biological role of core+1/ARFP, as well as the transcriptional modulation of hepcidin, the main regulator of iron metabolism.
Ioannis Karakasiliotis - One of the best experts on this subject based on the ideXlab platform.
-
hepatitis c virus core 1 ARF Protein modulates the cyclin d1 prb pathway and promotes carcinogenesis
Journal of Virology, 2018Co-Authors: Savvina Moustafa, Ioannis Karakasiliotis, Penelope MavromaraAbstract:Viruses often encompass overlapping reading frames and unconventional translation mechanisms in order to maximize the output from a minimum genome and to orchestrate their timely gene expression. Hepatitis C virus (HCV) possesses such an unconventional open reading frame (ORF) within the core-coding region, encoding an additional Protein, initially designated ARFP, F, or core+1. Two predominant isoforms of core+1/ARFP have been reported, core+1/L, initiating from codon 26, and core+1/S, initiating from codons 85/87 of the polyProtein coding region. The biological significance of core+1/ARFP expression remains elusive. The aim of the present study was to gain insight into the functional and pathological properties of core+1/ARFP through its interaction with the host cell, combining in vitro and in vivo approaches. Our data provide strong evidence that the core+1/ARFP of HCV-1a stimulates cell proliferation in Huh7-based cell lines expressing either core+1/S or core+1/L isoforms and in transgenic liver disease mouse models expressing core+1/S Protein in a liver-specific manner. Both isoforms of core+1/ARFP increase the levels of cyclin D1 and phosphorylated Rb, thus promoting the cell cycle. In addition, core+1/S was found to enhance liver regeneration and oncogenesis in transgenic mice. The induction of the cell cycle together with increased mRNA levels of cell proliferation-related oncogenes in cells expressing the core+1/ARFP Proteins argue for an oncogenic potential of these Proteins and an important role in HCV-associated pathogenesis.IMPORTANCE This study sheds light on the biological importance of a unique HCV Protein. We show here that core+1/ARFP of HCV-1a interacts with the host machinery, leading to acceleration of the cell cycle and enhancement of liver carcinogenesis. This pathological mechanism(s) may complement the action of other viral Proteins with oncogenic properties, leading to the development of hepatocellular carcinoma. In addition, given that immunological responses to core+1/ARFP have been correlated with liver disease severity in chronic HCV patients, we expect that the present work will assist in clarifying the pathophysiological relevance of this Protein as a biomarker of disease progression.
-
High prevalence of antibodies to core+1/ARF Protein in HCV-infected patients with advanced cirrhosis.
The Journal of general virology, 2017Co-Authors: Katerina Kassela, Ioannis Karakasiliotis, Stefanos Charpantidis, John Koskinas, Theodora Mylopoulou, Konstantinos Mimidis, Christoph Sarrazin, Georgios Grammatikos, Penelope MavromaraAbstract:Hepatitis C virus (HCV) possesses a second open reading frame (ORF) within the core gene encoding an additional Protein, known as the alternative reading frame Protein (ARFP), F or core+1. The biological significance of the core+1/ARF Protein remains elusive. However, several independent studies have shown the presence of core+1/ARFP antibodies in chronically HCV-infected patients. Furthermore, a higher prevalence of core+1/ARFP antibodies was detected in patients with HCV-associated hepatocellular carcinoma (HCC). Here, we investigated the incidence of core+1/ARFPantibodies in chronically HCV-infected patients at different stages of cirrhosis in comparison to chronically HCV-infected patients at earlier stages of disease. Using ELISA, we assessed the prevalence of anti-core+1 antibodies in 30 patients with advanced cirrhosis [model for end-stage liver disease (MELD) ≥15] in comparison with 50 patients with mild cirrhosis (MELD
-
high prevalence of antibodies to core 1 ARF Protein in hcv infected patients with advanced cirrhosis
Journal of General Virology, 2017Co-Authors: Ioannis Karakasiliotis, Katerina Kassela, Stefanos Charpantidis, John Koskinas, Theodora Mylopoulou, Konstantinos Mimidis, Christoph Sarrazin, Georgios GrammatikosAbstract:Hepatitis C virus (HCV) possesses a second open reading frame (ORF) within the core gene encoding an additional Protein, known as the alternative reading frame Protein (ARFP), F or core+1. The biological significance of the core+1/ARF Protein remains elusive. However, several independent studies have shown the presence of core+1/ARFP antibodies in chronically HCV-infected patients. Furthermore, a higher prevalence of core+1/ARFP antibodies was detected in patients with HCV-associated hepatocellular carcinoma (HCC). Here, we investigated the incidence of core+1/ARFPantibodies in chronically HCV-infected patients at different stages of cirrhosis in comparison to chronically HCV-infected patients at earlier stages of disease. Using ELISA, we assessed the prevalence of anti-core+1 antibodies in 30 patients with advanced cirrhosis [model for end-stage liver disease (MELD) ≥15] in comparison with 50 patients with mild cirrhosis (MELD <15) and 164 chronic HCV patients without cirrhosis. 28.7 % of HCV patients with cirrhosis were positive for anti-core+1 antibodies, in contrast with 16.5 % of non-cirrhotic HCV patients. Moreover, there was significantly higher positivity for anti-core+1 antibodies in HCV patients with advanced cirrhosis (36.7 %) compared to those with early cirrhosis (24 %) (P<0.05). These findings, together with the high prevalence of anti-core+1 antibodies in HCV patients with HCC, suggest that core+1 Protein may have a role in virus-associated pathogenesis, and provide evidence to suggest that the levels of anti-core+1 antibodies may serve as a marker for disease progression.
-
expression of the novel hepatitis c virus core 1 ARF Protein in the context of jfh1 based replicons
Journal of Virology, 2015Co-Authors: Ioly Kottaloizou, Ioannis Karakasiliotis, Niki Vassilaki, Panagiotis Sakellariou, Ralf Bartenschlager, Penelope MavromaraAbstract:Hepatitis C virus contains a second open reading frame within the core gene, designated core+1/ARF. Here we demonstrate for the first time expression of core+1/ARF Protein in the context of a bicistronic JFH1-based replicon and report the production of two isoforms, core+1/L (long) and core+1/S (short), with different kinetics.
-
Expression of the Novel Hepatitis C Virus Core+1/ARF Protein in the Context of JFH1-Based Replicons
Journal of virology, 2015Co-Authors: Ioly Kotta-loizou, Ioannis Karakasiliotis, Niki Vassilaki, Panagiotis Sakellariou, Ralf Bartenschlager, Penelope MavromaraAbstract:Hepatitis C virus contains a second open reading frame within the core gene, designated core+1/ARF. Here we demonstrate for the first time expression of core+1/ARF Protein in the context of a bicistronic JFH1-based replicon and report the production of two isoforms, core+1/L (long) and core+1/S (short), with different kinetics.
Paule Seite - One of the best experts on this subject based on the ideXlab platform.
-
Human tumor suppressor p14ARF negatively regulates rRNA transcription and inhibits UBF1 transcription factor phosphorylation
Oncogene, 2006Co-Authors: Olivier Ayrault, Laetitia Andrique, D Fauvin, B Eymin, Sylvie Gazzeri, Paule SeiteAbstract:The nucleolar ARF Protein has been shown to regulate cell cycle through both p53-dependent and -independent pathways. In addition to the well-characterized ARF-mdm2-p53 pathway, several partners of ARF have recently been described that could participate in alternative regulation process. Among those is the nucleolar Protein B23/NPM, involved in the sequential maturation of rRNA. p19ARF can interact with B23/NPM in high molecular complexes and partially inhibit the cleavage of the 32S rRNA, whereas the human p14ARF Protein has been shown to participate in the degradation of NPM/B23 by the proteasome. These data led to define ARF as a negative regulator of ribosomal RNA maturation. Our recent finding that the human p14ARF Protein was able to specifically interact with the rRNA promoter in a p53-independent context, led us to analyse in vitro and in vivo the consequences of this interaction. Luciferase assay and pulse-chase experiments demonstrated that the rRNA transcription was strongly reduced upon p14ARF overexpression. Investigations on potential interactions between p14ARF and the transcription machinery Proteins demonstrated that the upstream binding factor (UBF), required for the initiation of the transcriptional complex, was a new partner of the p14ARF Protein. We next examined the phosphorylation status of UBF as UBF phosphorylation is required to recruit on the promoter factors involved in the transcriptional complex. Upon p14ARF overexpression, UBF was found hypophosphorylated, thus unable to efficiently recruit the transcription complex. Taken together, these data define a new p53-independent pathway that could regulate cell cycle through the negative control of rRNA transcription.
-
In vitro and in vivo analysis of the interaction between 5.8S rRNA and ARF Protein reveal a new difference between murine p19ARF and human p14ARF.
Oncogene, 2005Co-Authors: Laetitia Andrique, Olivier Ayrault, Christian-jacques Larsen, Paule SeiteAbstract:Both human and murine ARF Proteins have been recently reported to impair rRNA maturation and ribosomes biogenesis through a p53-independent pathway. A specific interaction has been established between 5.8S rRNA and the murine p19ARF specie. We report here, by use of both in vitro and ChIP-RNA assays, the absence of any interaction between the human p14ARF and the homologous 5.8S rRNA. Our data are not consistent with the involvement of a 5.8S–p14ARF complex in ribosome biogenesis in man. Rather they suggest that the human Protein does not require such an interaction to achieve a similar function. This result is a new argument in favour of functional differences between human and murine ARF Proteins.
-
Human ARF tumor suppressor specifically interacts with chromatin containing the promoter of rRNA genes
Oncogene, 2004Co-Authors: Olivier Ayrault, Laetitia Andrique, Christian-jacques Larsen, Paule SeiteAbstract:The tumor suppressor ARF (Alternative Reading Frame) Protein (p14^ARF in human and p19^ARF in mouse) is mainly located in the nucleolus consistent with its subcellular localization, the Protein has been shown to specifically interact with 5.8S rRNA and with B23/Nucleophosmin and to regulate ribosome biogenesis. Here, we show that the p14^ARF Protein interacts with chromatin and is recovered by chromatin immunoprecipitation (ChIP) in a fraction that contains a DNA sequence of the rRNA gene promoter. In addition, topoisomerase I (Topo I) that has been shown to interact with p14^ARF coprecipitates with p14^ARF containing chromatin. These data, in view of the function for Topo I in rRNA transcription, are consistent with a role for the p14^ARF-Topo I complex in rRNA transcription and/or maturation.
-
Human ARF Protein interacts with topoisomerase I and stimulates its activity.
Oncogene, 2001Co-Authors: Lucie Karayan, Paule Seite, Jean-françois Riou, Julien Migeon, Anne Cantereau, Christian-jacques LarsenAbstract:The ARF gene (p19ARF in mouse and p14ARF in man) has become a central actor of the cell cycle regulation process as it participates to the ARF-MDM2-p53 pathway and the Rb-E2F-1 pathway. By use of immunoprecipitation and Western blotting (IP/WB), we now show that ARF physically associates with Topoisomerase I (Topo I). ARF-Topo I immune complexes were detected in SF9 insect cells infected with recombinant baculoviruses encoding the two genes as well as in 293 cells that express endogeneously these Proteins. Preparations of a GST–ARF recombinant Protein stimulated the DNA relaxation activity of Topo I but, in contrast, had no effect on the decatenation activity of Topo II. The Topo I stimulation was also detected in cell extracts of SF9 cells expressing both Proteins. A confocal microscopy study indicated that part of ARF and Topo I colocalized in the granular component structure of the nucleolus. As a whole, our data indicate that Topo I is a new partner of ARF and suggest that ARF is involved in cell reactions that require Topo I.
Philippe Chavrier - One of the best experts on this subject based on the ideXlab platform.
-
ARF Proteins: roles in membrane traffic and beyond
Nature Reviews Molecular Cell Biology, 2006Co-Authors: Crislyn D'souza-schorey, Philippe ChavrierAbstract:The ADP-ribosylation factor (ARF) small GTPases regulate vesicular traffic and organelle structure by recruiting coat Proteins, regulating phospholipid metabolism and modulating the structure of actin at membrane surfaces. Recent advances in our understanding of the signalling pathways that are regulated by ARF1 and ARF6, two of the best characterized ARF Proteins, provide a molecular context for ARF Protein function in fundamental biological processes, such as secretion, endocytosis, phagocytosis, cytokinesis, cell adhesion and tumour-cell invasion. ADP-ribosylation factor (ARF) Proteins regulate membrane trafficking and actin remodelling along the secretory and endocytic pathways. However, recent evidence has revealed that the function of ARF Proteins can influence cellular processes such as phagocytosis, cell division and tumour-cell invasion. The unique cellular distribution of individual ADP-ribosylation factor (ARF) Proteins and the molecules with which they interact are vital in dictating ARF-Protein function. The mutually exclusive properties in cellular distribution and function of mammalian ARF1 and ARF6 have been extensively investigated. However, parallels in the cellular roles of both these ARF Proteins in vesicle budding and actin remodelling is becoming increasingly evident. ARF1–GTP drives COPI-mediated vesicle budding along the biosynthetic and secretory pathway. ARF1 also regulates the formation of clathrin-coated vesicles at the trans -Golgi network by promoting the recruitment of adaptor-Protein complexes AP-1, AP-3, AP-4, and the GGAs from the cytosol onto membranes. ARF1 activation has been shown to stimulate the assembly of spectrin and the actin cytoskeleton on Golgi membranes. Nucleotide exchange on ARF is regulated by the Sec7-domain-containing GEFs. Site-specific targeting of GBF- and BIG-family GEFs to Golgi subcompartments might have a prominent role in the formation of coats at specific locations. Membrane lipid composition and temporal aspects of vesicle budding can affect the targeting of ARF1 to Golgi membranes. GTP hydrolysis on ARF1 is required for the dissociation of coat Proteins from transport vesicles, and is mediated by a family of ARF GAPs. GTP-hydrolysis on ARF1 is also required for cargo packaging, and ARF GAPs might function to couple cargo sorting with vesicle formation. ARF6 localizes to the plasma membrane and endosomal compartments, in which it regulates clathrin-dependent endocytic membrane trafficking, as well as the trafficking and sorting of molecules that lack cytoplasmic AP-2 and clathrin sorting sequences, through a unique endocytic route. ARF6 has also been implicated in actin remodelling at the cell periphery. The effects of ARF6 on the actin cytoskeleton are thought to occur through the activation of the Rac1 GTPase and/or its effect on phopholipid metabolism. The ARF6-GTPase cycle can impinge on several cellular events that require rapid changes in cell-surface morphology and as such, directly impinges on cellular processes such as phagocytosis, cell–cell adhesion, cell migration, tumour-cell invasion and cytokinesis.
-
ARF Proteins: roles in membrane traffic and beyond.
Nature reviews. Molecular cell biology, 2006Co-Authors: Crislyn D'souza-schorey, Philippe ChavrierAbstract:The ADP-ribosylation factor (ARF) small GTPases regulate vesicular traffic and organelle structure by recruiting coat Proteins, regulating phospholipid metabolism and modulating the structure of actin at membrane surfaces. Recent advances in our understanding of the signalling pathways that are regulated by ARF1 and ARF6, two of the best characterized ARF Proteins, provide a molecular context for ARF Protein function in fundamental biological processes, such as secretion, endocytosis, phagocytosis, cytokinesis, cell adhesion and tumour-cell invasion.
-
ARNO3, a Sec7-domain guanine nucleotide exchange factor for ADP ribosylation factor 1, is involved in the control of Golgi structure and function
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: Michel Franco, Bruno Goud, Joëlle Boretto, Sylviane Robineau, Solange Monier, Pierre Chardin, Philippe ChavrierAbstract:Budding of transport vesicles in the Golgi apparatus requires the recruitment of coat Proteins and is regulated by ADP ribosylation factor (ARF) 1. ARF1 activation is promoted by guanine nucleotide exchange factors (GEFs), which catalyze the transition to GTP-bound ARF1. We recently have identified a human Protein, ARNO (ARF nucleotide-binding-site opener), as an ARF1-GEF that shares a conserved domain with the yeast Sec7 Protein. We now describe a human Sec7 domain-containing GEF referred to as ARNO3. ARNO and ARNO3, as well as a third GEF called cytohesin-1, form a family of highly related Proteins with identical structural organization that consists of a central Sec7 domain and a carboxy-terminal pleckstrin homology domain. We show that all three Proteins act as ARF1 GEF in vitro, whereas they have no effect on ARF6, an ARF Protein implicated in the early endocytic pathway. Substrate specificity of ARNO-like GEFs for ARF1 depends solely on the Sec7 domain. Overexpression of ARNO3 in mammalian cells results in (i) fragmentation of the Golgi apparatus, (ii) redistribution of Golgi resident Proteins as well as the coat component β-COP, and (iii) inhibition of SEAP transport (secreted form of alkaline phosphatase). In contrast, the distribution of endocytic markers is not affected. This study indicates that Sec7 domain-containing GEFs control intracellular membrane compartment structure and function through the regulation of specific ARF Proteins in mammalian cells.
Ioly Kottaloizou - One of the best experts on this subject based on the ideXlab platform.
-
expression of the novel hepatitis c virus core 1 ARF Protein in the context of jfh1 based replicons
Journal of Virology, 2015Co-Authors: Ioly Kottaloizou, Ioannis Karakasiliotis, Niki Vassilaki, Panagiotis Sakellariou, Ralf Bartenschlager, Penelope MavromaraAbstract:Hepatitis C virus contains a second open reading frame within the core gene, designated core+1/ARF. Here we demonstrate for the first time expression of core+1/ARF Protein in the context of a bicistronic JFH1-based replicon and report the production of two isoforms, core+1/L (long) and core+1/S (short), with different kinetics.
-
evolutionary and functional studies on the novel hepatitis c virus core 1 ARF Protein
IWBBIO, 2014Co-Authors: Ioly KottaloizouAbstract:Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and hepatocellular carcinoma (HCC). HCV is an enveloped positivestranded RNA virus, belonging to the Flaviviridae family. The HCV genome produces a polyProtein precursor which is processed by proteases and yields at least 10 Proteins. HCV possesses a second open reading frame (ORF) within the core gene, encoding an intrinsically disordered Protein known as core+1/ARFP. Core+1/ARFP has been implicated in HCC and there is evidence that it acts as a modulator; however, its function in the context of the HCV life cycle still remains elusive. The aim of this study was to gain insight into the biological role of core+1/ARFP. To this end, a dataset of 4428 core+1/ARF amino acid sequences from 18 confirmed HCV subtypes was constructed. As shown before, core+1/ARF ORF is present in all subtypes and its length is subtype-dependent. Furthermore, core+1/ARFP is less conserved than core but at least as conserved as the HCV non-structural (NS) 2 Protein. Subsequently, 24 exemplar core+1/ARF amino acid sequences, one or two from each subtype, were used for further analysis. Compositional profiling of core+1/ARFP revealed an enrichment in both disorder-promoting and high-degeneracy residues; the latter a tendency of overlapping genes. Phylogenetic analysis of the Flaviviridae family supports the notion that core+1/ARF ORF originated de novo by overprinting within the ancestral core gene and estimation of selection constraint indicates that core+1/ARF ORF is under weak purifying selection. In addition, Hidden Markov Models (HMMs) revealed an interesting similarity between core+1/ARFP and the RNA-binding amino-terminal domain of core, which suggests that core+1/ARFP may also be an RNA-binding Protein. Subsequently, core+1/ARF amino acid sequences were assessed using the Eukaryotic Linear Motif (ELM) database for the presence of Protein binding and modification motifs conserved in all HCV subtypes. Finally, both Protein-Protein interaction and transcriptional regulation networks were generated using Cytoscape, based on data derived from the literature, and their analysis revealed that core+1/ARFP is implicated in regulation and response to external stimuli and stress, as well as in major signaling pathways known to play a role in HCC. In conclusion, this study provides insight into the molecular evolution of core+1/ARFP. Moreover, the modulatory role of core+1/ARFP is confirmed and expanded as new putative targets are identified – to be experimentally verified in the future – and core+1/ARFP’s association with HCC is elaborated. Proceedings IWBBIO 2014. Granada 7-9 April, 2014 204
-
hepatitis c virus core 1 ARF Protein decreases hepcidin transcription through an ap1 binding site
Journal of General Virology, 2013Co-Authors: Ioly Kottaloizou, Niki Vassilaki, Ralf Bartenschlager, George Pissas, Athanassios Kakkanas, Latifa Bakiri, Penelope MavromaraAbstract:Chronic viral hepatitis C is characterized by iron accumulation in the liver, and hepcidin regulates iron absorption. Hepatitis C virus (HCV) core+1/ARFP is a novel Protein produced by a second functional ORF within the core gene. Here, using reporter assays and HCV bicistronic replicons, we show that, similarly to core, core+1/ARFP decreases hepcidin expression in hepatoma cells. The activator Protein 1 (AP1) binding site of the human hepcidin promoter, shown here to be relevant to basal promoter activity and to the repression by core, is essential for the downregulation by core+1/ARFP while the previously described C/EBP (CCAAT/enhancer binding Protein) and STAT (signal transducer and activator of transcription) sites are not. Consistently, expression of the AP1 components c-jun and c-fos obliterated the repressive effect of core and core+1/ARFP. In conclusion, we provide evidence that core+1/ARFP downregulates AP1-mediated transcription, providing new insights into the biological role of core+1/ARFP, as well as the transcriptional modulation of hepcidin, the main regulator of iron metabolism.