ORCID Profile
0000-0002-6085-8936
Current Organisation
University of Adelaide
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Publisher: Cold Spring Harbor Laboratory
Date: 15-06-2002
DOI: 10.1101/GAD.991402
Abstract: Mammalian cells adapt to hypoxic conditions through a transcriptional response pathway mediated by the hypoxia-inducible factor, HIF. HIF transcriptional activity is suppressed under normoxic conditions by hydroxylation of an asparagine residue within its C-terminal transactivation domain, blocking association with coactivators. Here we show that the protein FIH-1, previously shown to interact with HIF, is an asparaginyl hydroxylase. Like known hydroxylase enzymes, FIH-1 is an Fe(II)-dependent enzyme that uses molecular O 2 to modify its substrate. Together with the recently discovered prolyl hydroxylases that regulate HIF stability, this class of oxygen-dependent enzymes comprises critical regulatory components of the hypoxic response pathway.
Publisher: Elsevier BV
Date: 05-1998
DOI: 10.1016/S0092-8674(00)81432-4
Abstract: We demonstrate that mice lacking the oxysterol receptor, LXR alpha, lose their ability to respond normally to dietary cholesterol and are unable to tolerate any amount of cholesterol in excess of that which they synthesize de novo. When fed diets containing cholesterol, LXR alpha (-/-) mice fail to induce transcription of the gene encoding cholesterol 7alpha-hydroxylase (Cyp7a), the rate-limiting enzyme in bile acid synthesis. This defect is associated with a rapid accumulation of large amounts of cholesterol in the liver that eventually leads to impaired hepatic function. The regulation of several other crucial lipid metabolizing genes is also altered in LXR alpha (-/-) mice. These results demonstrate the existence of a physiologically significant feed-forward regulatory pathway for sterol metabolism and establish the role of LXR alpha as the major sensor of dietary cholesterol.
Publisher: Elsevier
Date: 2004
Publisher: Wiley
Date: 07-11-2014
DOI: 10.1111/CEO.12462
Abstract: The retina, like many cancers, produces energy from glycolysis even in the presence of oxygen. This phenomenon is known as aerobic glycolysis and eponymously as the Warburg effect. In recent years, the Warburg effect has become an explosive area of study within the cancer research community. The expanding knowledge about the molecular mechanisms underpinning the Warburg effect in cancer promises to provide a greater understanding of mammalian retinal metabolism and has motivated cancer researchers to target the Warburg effect as a novel treatment strategy for cancer. However, if the molecular mechanisms underlying the Warburg effect are shared by the retina and cancer, treatments targeting the Warburg effect may have serious adverse effects on retinal metabolism. Herein, we provide an updated understanding of the Warburg effect in mammalian retina.
Publisher: Springer Science and Business Media LLC
Date: 22-11-2013
DOI: 10.1038/NRC3621
Abstract: Mammalian basic HLH (helix-loop-helix)-PER-ARNT-SIM (bHLH-PAS) proteins are heterodimeric transcription factors that sense and respond to environmental signals (such as pollutants) or to physiological signals (for ex le, hypoxia and circadian rhythms) through their two PAS domains. PAS domains form a generic three-dimensional fold, which commonly contains an internal cavity capable of small-molecule binding and outer surfaces adept at protein-protein interactions. These proteins are important in several pro-tumour and antitumour pathways and their activities can be modulated by both natural metabolites and oncometabolites. Recently determined structures and successful small-molecule screening programmes are now providing new opportunities to discover selective agonists and antagonists directed against this multitasking family of transcription factors.
Publisher: Cold Spring Harbor Laboratory
Date: 17-01-2017
DOI: 10.1101/101022
Abstract: Kinesin-1 is a nanoscale molecular motor that walks towards the fast growing (plus) ends of microtubules (MTs), hauling molecular cargo to specific reaction sites in cells. Kinesin-driven transport is central to the self-organisation of eukaryotic cells and shows great promise as a tool for nano-engineering 1 , 2 . Recent work hints that kinesin may also play a role in modulating the stability of its MT track, both in vitro 3 - 5 and in vivo 6 , but results are conflicting 7 - 9 and mechanisms are unclear. Here we report a new dimension to the kinesin-MT interaction, whereby strong-state (ATP-bound and apo) kinesin-1 motor domains inhibit the shrinkage of GDP-MTs by up to 2 orders of magnitude and expand their lattice spacing by ~1.6%. Our data reveal an unexpected new mechanism by which the mechanochemical cycles of kinesin and tubulin interlock, allowing motile kinesins to influence the structure, stability and mechanics of their MT track.
Publisher: Elsevier BV
Date: 09-2003
Publisher: MDPI AG
Date: 19-10-2023
DOI: 10.3390/BIOM13101545
Publisher: Proceedings of the National Academy of Sciences
Date: 04-03-2008
Abstract: Cells adapt to hypoxia by a cellular response, where hypoxia-inducible factor 1α (HIF-1α) becomes stabilized and directly activates transcription of downstream genes. In addition to this “canonical” response, certain aspects of the pathway require integration with Notch signaling, i.e., HIF-1α can interact with the Notch intracellular domain (ICD) to augment the Notch downstream response. In this work, we demonstrate an additional level of complexity in this cross-talk: factor-inhibiting HIF-1 (FIH-1) regulates not only HIF activity, but also the Notch signaling output and, in addition, plays a role in how Notch signaling modulates the hypoxic response. We show that FIH-1 hydroxylates Notch ICD at two residues (N 1945 and N 2012 ) that are critical for the function of Notch ICD as a transactivator within cells and during neurogenesis and myogenesis in vivo . FIH-1 negatively regulates Notch activity and accelerates myogenic differentiation. In its modulation of the hypoxic response, Notch ICD enhances recruitment of HIF-1α to its target promoters and derepresses HIF-1α function. Addition of FIH-1, which has a higher affinity for Notch ICD than for HIF-1α, abrogates the derepression, suggesting that Notch ICD sequesters FIH-1 away from HIF-1α. In conclusion, the data reveal posttranslational modification of the activated form of the Notch receptor and an intricate mode of cross-coupling between the Notch and hypoxia signaling pathways.
Publisher: Elsevier BV
Date: 04-2005
Publisher: Elsevier BV
Date: 08-2006
Publisher: Wiley
Date: 16-08-2020
DOI: 10.1111/CEO.13833
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-01-2016
Abstract: Like cancer cells, photoreceptor cells produce lactate aerobically, requiring lactate dehydrogenase A (LDH-A). Cancer cells also use glycolytic intermediates for biosynthesis. The molecular switch controlling glycolytic flow is thought to be an isoenzyme of pyruvate kinase (PKM2). Here, we determined the expression and localization of PKM2 and LDH-A in mammalian retina and make comparisons with the brain. Single- and double-labeling immunohistochemistry for PKM2, pyruvate kinase M1 (PKM1), and LDH-A were performed using retinal sections from C57BL/6 mice, Sprague-Dawley rats, rabbits, marmosets, and humans. Pyruvate kinase M1 and PKM2 mRNA and protein expression levels were quantified in rodent retina and brain by using qPCR and immunoblotting. The quaternary forms of PKM2 in rat retina were also determined. Pyruvate kinase M2 was present in some glial cells and rod and cone photoreceptors in the retina of all species but was exclusively localized to glia in the brain. Pyruvate kinase M1 was confined to neurons in the retina and brain. Lactate dehydrogenase A was principally found in photoreceptors and inner portion of the avascular rabbit retina. Western blotting and qPCR confirmed high levels of PKM2 and LDH-A in the retina. There was a 6- to 9-fold greater expression of PKM2 mRNA in the rodent retina than in the brain. Both the dimeric (inactive, biosynthesis-driving form) and the active tetrameric (glycolytic-driving) forms of PKM2 were present in retina but not in brain. Mammalian photoreceptors contain dimeric and tetrameric PKM2 and LDH-A. This is consistent with the ability to switch between energy production and biosynthesis like a proliferating tissue, possibly due to demands of opsin synthesis.
Publisher: MDPI AG
Date: 27-03-2017
DOI: 10.3390/PH10020035
Publisher: Informa UK Limited
Date: 26-05-2015
Publisher: Public Library of Science (PLoS)
Date: 07-09-2012
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.EXER.2019.01.013
Abstract: Müller cells (MCs) play a crucial role in the retina, and cultured MC lines are an important tool with which to study MC function. Transformed MC lines have been widely used however, the transformation process can also lead to unwanted changes compared to the primary cells from which they were derived. To provide an alternative experimental tool, a novel monoclonal spontaneously immortalized rat Müller cell line, SIRMu-1, was derived from primary rat MCs and characterized. Immunofluorescence, western blotting and RNA sequencing demonstrate that the SIRMu-1 cell line retains similar characteristics to cultured primary MCs in terms of expression of the MC markers cellular retinaldehyde-binding protein, glutamine synthetase, S100, vimentin and glial fibrillary acidic protein at both the mRNA and protein levels. Both the cellular morphology and overall transcriptome of the SIRMu-1 cells are more similar to primary rat MCs than the commonly used rMC-1 cells, a well-described, transformed rat MC line. Furthermore, SIRMu-1 cells proliferate rapidly, have an effectively indefinite life span and a high transfection efficiency. The expression of Y chromosome specific genes confirmed that the SIRMu-1 cells are derived from male MCs. Thus, the SIRMu-1 cell line represents a valuable experimental tool to study roles of MCs in both physiological and pathological states.
Publisher: Elsevier BV
Date: 07-10-2010
DOI: 10.1016/J.MCE.2010.06.008
Abstract: Hypoxia inducible factors (HIFs) are transcription factors that mediate physiological responses to hypoxia. Hypoxia is established as the major inducer of HIFs, but stimuli such as transition metals and hormones also induce HIF target genes. Whilst the ovarian granulosa cell layer is known to be avascular and the follicle is vascularised via the thecal cell layer, little is known about the role of hypoxia or HIFs in regulating ovarian function. In this study, we hypothesized that hypoxia as well as non-hypoxic stimuli cooperate in promoting follicle differentiation and luteinization via HIF activity and resultant gene regulation. We quantitatively measured the HIF1alpha protein response to hCG in ovarian granulosa cell cultures and in vivo and developed a transgenic (HRE(4)-SV40-EGFP) HIF reporter mouse line. We observed a time-dependent increase of HIF1alpha protein levels in granulosa cells post-hCG in vivo, maximal around time of ovulation. hCG alone was unable to promote HIF1alpha protein accumulation in cultured granulosa cells, but increased protein abundance was observed when combined with a hypoxic stimulus. HRE-EGFP ovaries showed no follicular EGFP in stages prior to antrum formation. However, HIF regulated EGFP was maximally induced in granulosa cells around the time of ovulation and readily observed in corpora lutea. There was also an increase in HIF regulated EGFP activity in the corpora lutea from functional to regressing stages. Taken together, these observations establish the notion that HIFs play a role during follicular differentiation and luteinization.
Publisher: Springer Science and Business Media LLC
Date: 17-03-2008
Publisher: Wiley
Date: 18-08-2016
DOI: 10.1111/FEBS.13824
Abstract: Transcription factors of the basic helix-loop-helix (bHLH) PER-ARNT-SIM (PAS) family generally have critical and nonredundant biological roles, but some bHLH PAS proteins compete for common cofactors or recognise similar DNA elements. Identifying factors that regulate function of bHLH PAS proteins, particularly in cells where multiple family members are coexpressed, is important for understanding bHLH PAS factor biology. This study identifies and characterises a novel interaction between melanoma-associated antigen D1 (MAGED1) and select members of the bHLH PAS transcription factor family. MAGED1 binds and positively regulates the transcriptional activity of family members SIM1, SIM2, NPAS4 and ARNT2, but does not interact with AhR, HIF1α and ARNT. This interaction is mediated by PAS repeat regions which also form the interface for bHLH PAS dimerisation, and accordingly MAGED1 is not found in complex with bHLH PAS dimers. We show that MAGED1 does not affect bHLH PAS protein levels and cannot be acting as a coactivator of transcriptionally active heterodimers, but rather appears to interact with nascent bHLH PAS proteins in the cytoplasm to enhance their function prior to nuclear import. As a selective regulator, MAGED1 may play an important role in the biology of these specific factors and in general bHLH PAS protein dynamics.
Publisher: eLife Sciences Publications, Ltd
Date: 12-09-2019
DOI: 10.7554/ELIFE.50585
Abstract: Cells rely on prolyl hydroxylase enzymes to sense low levels of oxygen, but they might act on fewer targets than previously thought.
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.YEXCR.2017.03.030
Abstract: The hypoxia inducible factors (HIFs) promote changes in gene expression in response to hypoxia, and mediate key physiological responses such as angiogenesis. They play important roles in development and normal physiology, as well as in ischaemic and other pathologies. The human eye is a complex organ, with tight regulation of vascularisation and oxygen delivery, with the highly specialised retina containing both highly vascularised and avascular regions. This review, written to honour the significant contribution of Lorenz Poellinger to this field, covers the role of the HIFs in normal development of the eye, specifically the vasculature, as well as their roles in numerous retinal pathologies, including ischaemic retinopathies, and age-related macular degeneration (AMD). The characterisation of the HIFs in the eye has improved our understanding of the development, function, and numerous pathologies of the eye, and should inform future therapeutic approaches.
Publisher: Springer Science and Business Media LLC
Date: 2012
Publisher: Elsevier BV
Date: 04-2004
Publisher: Public Library of Science (PLoS)
Date: 29-04-2019
Publisher: Public Library of Science (PLoS)
Date: 11-01-2016
Publisher: American Society for Clinical Investigation
Date: 17-06-2013
DOI: 10.1172/JCI68035
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.BIOCEL.2009.01.005
Abstract: FIH-1, factor inhibiting hypoxia-inducible factor-1 (HIF-1), regulates oxygen sensing by hydroxylating an asparagine within HIF-alpha. It also hydroxylates asparagines in many proteins containing ankyrin repeats, including Notch1-3, p105 and I?B?. Relative binding affinity and hydroxylation rate are crucial determinants of substrate selection and modification. We determined the contributions of substrate sequence composition and length and of oxygen concentration to the FIH-1-binding and/or hydroxylation of Notch1-4 and compared them with those for HIF-1alpha. We also demonstrated hydroxylation of two asparagines in Notch2 and 3, corresponding to Sites 1 and 2 of Notch1, by mass spectrometry for the first time. Our data demonstrate that substrate length has a much greater influence on FIH-1-dependent hydroxylation of Notch than of HIF-1alpha, predominantly through binding affinity rather than maximal reaction velocity. The K(m) value of FIH-1 for Notch1, < 0.2 microM, is at least 250-fold lower than that of 50 microM for HIF-1alpha. Site 1 of Notch1-3 appeared the preferred site of FIH-1 hydroxylation in these substrates. Interestingly, binding of Notch4 to FIH-1 was observed with an affinity almost 10-fold lower than for Notch1-3, but no hydroxylation was detected. Importantly, we demonstrate that the K(m) of FIH-1 for oxygen at the preferred Site 1 of Notch1-3, 10-19 microM, is an order of magnitude lower than that for Site 2 or HIF-1alpha. Hence, at least during in vitro hydroxylation, Notch is likely to become efficiently hydroxylated by FIH-1 even under relatively severe hypoxic conditions, where HIF-1alpha hydroxylation would be reduced.
Publisher: Springer Science and Business Media LLC
Date: 18-01-2008
Abstract: The hypoxia-inducible factors (HIFs) are critical for cellular adaptation to limiting oxygen and regulate a wide array of genes when cued by cellular oxygen-sensing mechanisms. HIF is able to direct transcription from either of two transactivation domains, each of which is regulated by distinct mechanisms. The oxygen-dependent asparaginyl hydroxylase factor-inhibiting HIF-1alpha (FIH-1) is a key regulator of the HIF C-terminal transactivation domain, and provides a direct link between oxygen sensation and HIF-mediated transcription. Additionally, there are phosphorylation and nitrosylation events reported to modulate HIF transcriptional activity, as well as numerous transcriptional coactivators and other interacting proteins that together provide cell and tissue specificity of HIF target gene regulation.
Publisher: Springer Science and Business Media LLC
Date: 07-2003
DOI: 10.1007/S00018-003-2370-Y
Abstract: Oxygen depravation in mammals leads to the transcriptional induction of a host of target genes to metabolically adapt to this deficiency, including erythropoietin and vascular endothelial growth factor. This response is primarily mediated by the hypoxia-inducible factors (HIFs) which are members of the basic-helix-loop-helix/Per-ARNT-Sim (bHLH/PAS) transcription factor family. The HIFs are primarily regulated via a two-step mechanism of HIF post-translational modification, increasing both protein stability and transactivation capacity. This review aims to summarise our current understanding of these processes, and discuss the important role of the HIFs in the pathophysiology of many human diseases.
Publisher: Elsevier BV
Date: 06-1992
DOI: 10.1016/0305-0491(92)90135-E
Abstract: 1. Covalently-bound fatty acids were characterized in keratinous tissues obtained from a wide range of animals. 2. 18-Methyleicosanoic acid was a major component in all the mammalian fur s les examined except monotreme fur. In monotreme fur 26-carbon fatty acids predominated. 3. Fatty acids from feather keratin and reptile skin had different profiles to the alpha-keratins of mammalian fur. 4. The major forms of covalently-bound fatty acids are very similar in species that erged up to 125 million years ago.
Publisher: Wiley
Date: 2015
DOI: 10.1111/CEO.12493
Publisher: Portland Press Ltd.
Date: 10-07-2014
DOI: 10.1042/BJ20131618
Abstract: The bHLH (basic helix–loop–helix) PAS (Per/Arnt/Sim) transcription factor SIM1 (single-minded 1) is important for development and function of regions of the hypothalamus that regulate energy homoeostasis and the feeding response. Low-activity SIM1 variants have been identified in in iduals with severe early-onset obesity, but the underlying molecular causes of impaired function are unknown. In the present study we assess a number of human SIM1 variants with reduced activity and determine that impaired function is frequently due to defects in dimerization with the essential partner protein ARNT2 (aryl hydrocarbon nuclear translocator 2). Equivalent variants generated in the highly related protein SIM2 (single-minded 2) produce near-identical impaired function and dimerization defects, indicating that these effects are not unique to the structure of SIM1. On the basis of these data, we predict that other select SIM1 and SIM2 variants reported in human genomic databases will also be deficient in activity, and identify two new low-activity SIM1 variants (V290E and V326F) present in the population. The cumulative data is used in homology modelling to make novel observations about the dimerization interface between the PAS domains of SIM1 and ARNT2, and to define a mutational ‘hot-spot’ in SIM1 that is critical for protein function.
Publisher: Oxford University Press (OUP)
Date: 17-04-2013
DOI: 10.1093/NAR/GKT206
Publisher: The Company of Biologists
Date: 2014
DOI: 10.1242/JCS.158451
Abstract: Factor Inhibiting HIF (FIH) is an oxygen-dependent asparaginyl hydroxylase that regulates the hypoxia-inducible factors (HIFs). Several proteins containing ankyrin repeat domains have been characterised as substrates of FIH, although there is little evidence for a functional consequence of hydroxylation on these substrates. This study demonstrates that the transient receptor potential vanilloid 3 (TRPV3) channel is hydroxylated by FIH on asparagine 242 within the cytoplasmic ankyrin repeat domain. Hypoxia, FIH inhibitors and mutation of asparagine 242 all potentiated TRPV3-mediated current, without altering TRPV3 protein levels, indicating that oxygen-dependent hydroxylation inhibits TRPV3 activity. This novel mechanism of channel regulation by oxygen-dependent asparaginyl hydroxylation is likely to extend to other ion channels.
Publisher: American Society for Clinical Investigation
Date: 17-06-2013
DOI: 10.1172/JCI68016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-2002
Abstract: The hypoxia-inducible factors (HIFs) 1α and 2α are key mammalian transcription factors that exhibit dramatic increases in both protein stability and intrinsic transcriptional potency during low-oxygen stress. This increased stability is due to the absence of proline hydroxylation, which in normoxia promotes binding of HIF to the von Hippel–Lindau (VHL tumor suppressor) ubiquitin ligase. We now show that hypoxic induction of the COOH-terminal transactivation domain (CAD) of HIF occurs through abrogation of hydroxylation of a conserved asparagine in the CAD. Inhibitors of Fe(II)- and 2-oxoglutarate–dependent dioxygenases prevented hydroxylation of the Asn, thus allowing the CAD to interact with the p300 transcription coactivator. Replacement of the conserved Asn by Ala resulted in constitutive p300 interaction and strong transcriptional activity. Full induction of HIF-1α and -2α, therefore, relies on the abrogation of both Pro and Asn hydroxylation, which during normoxia occur at the degradation and COOH-terminal transactivation domains, respectively.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/RD13249
Abstract: Oxygen is an important component of the environment of the cumulus–oocyte complex (COC), both in vivo within the ovarian follicle and during in vitro oocyte maturation (IVM). Cumulus cells have a key role in supporting oocyte development, and cumulus cell function and gene expression are known to be altered when the environment of the COC is perturbed. Oxygen-regulated gene expression is mediated through the actions of the transcription factors, the hypoxia-inducible factors (HIFs). In the present study, the effect of oxygen on cumulus cell gene expression was examined following in vitro maturation of the murine COC at 2%, 5% or 20% oxygen. Increased expression of HIF-responsive genes, including glucose transporter-1, lactate dehydrogenase A and BCL2/adenovirus E1B interacting protein 3, was observed in cumulus cells matured at 2% or 5%, compared with 20% oxygen. Stabilisation of HIF1α protein in cumulus cells exposed to low oxygen was confirmed by western blot and HIF-mediated transcriptional activity was demonstrated using a transgenic mouse expressing green fluorescent protein under the control of a promoter containing hypoxia response elements. These results indicate that oxygen concentration influences cumulus cell gene expression and support a role for HIF1α in mediating the cumulus cell response to varying oxygen.
Publisher: Cold Spring Harbor Laboratory
Date: 02-02-2022
DOI: 10.1101/2022.02.01.475276
Abstract: The basic-Helix-Loop-Helix Per-Arnt-Sim (PAS) homology domain (bHLH-PAS) transcription factor (TF) family comprises critical biological sensors of physiological (hypoxia, tryptophan metabolites, neuronal activity, and appetite) and environmental (diet derived metabolites and environmental pollutants) stimuli to regulate genes involved in signal adaptation and homeostasis 1 . bHLH TFs bind DNA as homo or heterodimers via E-box (CANNTG) response elements, however the DNA binding specificity of the PAS domain-containing bHLH subfamily remains unresolved 1 . We systematically analysed cognate DNA binding hierarchies of prototypical bHLH-PAS family members (ARNT, ARNT2, HIF1α, HIF2α, AhR, NPAS4, SIM1) and demonstrate distinct core (NNCGTG) specificities for different heterodimer classes. The results also show that bHLH-PAS TFs bind over a large footprint 12-15bp and recognise preferential DNA sequences flanking the core. For ex le, specificity beyond otherwise identical core binding by SIM1 and the HIFs is mediated through N-terminal HIFα-DNA interactions. We also reveal an intimate relationship between DNA shape and both core and flanking TF binding allowing motif sequence flexibility and underpinning TF binding specificity. Furthermore, DNA-shape affinity relationships revealed that novel downstream PAS-A-loop DNA interactions are associated with AT-rich sequences that lead to high-affinity binding, and that loss of this function underpins a monogenic cause of human hyperphagic obesity in a recapitulated SIM1.R171H knock-in mouse model. Importantly, models of protein-DNA binding accurately predict in vivo occupancy, while response element methylation blocks DNA binding and predicts cell type specific chromatin occupancy. These data provide a definitive and accurate map of bHLH-PAS TF specificity and target selectivity through novel flanking protein-DNA interactions that are crucial for in vivo biological function.
Publisher: Elsevier
Date: 2002
Publisher: Elsevier BV
Date: 10-1998
DOI: 10.1016/S0959-437X(98)80013-0
Abstract: The liver X receptors (LXRs) are a family of transcription factors that were first identified as orphan members of the nuclear receptor superfamily. The identification of a specific class of oxidized derivatives of cholesterol as ligands for the LXRs has been crucial to helping understand the function of these receptors in vivo and first suggested their role in the regulation of lipid metabolism. Confirmation of this role has come from the recent analysis of LXR-deficient mice, which has demonstrated the essential function of one of these receptors in the liver as a major sensor of dietary cholesterol.
Publisher: SAGE Publications
Date: 1995
Publisher: Public Library of Science (PLoS)
Date: 17-01-2014
Publisher: American Society for Microbiology
Date: 2017
DOI: 10.1128/JVI.01430-16
Abstract: Hypoxia-inducible factor (HIF) is a transcriptional activator with a central role in regulating cellular responses to hypoxia. It is also emerging as a major target for viral manipulation of the cellular environment. Under normoxic conditions, HIF is tightly suppressed by the activity of oxygen-dependent prolyl and asparaginyl hydroxylases. The asparaginyl hydroxylase active against HIF, factor inhibiting HIF (FIH), has also been shown to hydroxylate some ankyrin repeat (ANK) proteins. Using bioinformatic analysis, we identified the five ANK proteins of the parapoxvirus orf virus (ORFV) as potential substrates of FIH. Consistent with this prediction, coimmunoprecipitation of FIH was detected with each of the ORFV ANK proteins, and for one representative ORFV ANK protein, the interaction was shown to be dependent on the ANK domain. Immunofluorescence studies revealed colocalization of FIH and the viral ANK proteins. In addition, mass spectrometry confirmed that three of the five ORFV ANK proteins are efficiently hydroxylated by FIH in vitro . While FIH levels were unaffected by ORFV infection, transient expression of each of the ORFV ANK proteins resulted in derepression of HIF-1α activity in reporter gene assays. Furthermore, ORFV-infected cells showed upregulated HIF target gene expression. Our data suggest that sequestration of FIH by ORFV ANK proteins leads to derepression of HIF activity. These findings reveal a previously unknown mechanism of viral activation of HIF that may extend to other members of the poxvirus family. IMPORTANCE The protein-protein binding motif formed from multiple repeats of the ankyrin motif is common among chordopoxviruses. However, information on the roles of these poxviral ankyrin repeat (ANK) proteins remains limited. Our data indicate that the parapoxvirus orf virus (ORFV) is able to upregulate hypoxia-inducible factor (HIF) target gene expression. This response is mediated by the viral ANK proteins, which sequester the HIF regulator FIH (factor inhibiting HIF). This is the first demonstration of any viral protein interacting directly with FIH. Our data reveal a new mechanism by which viruses reprogram HIF, a master regulator of cellular metabolism, and also show a new role for the ANK family of poxvirus proteins.
Publisher: Wiley
Date: 13-01-2008
Publisher: Wiley
Date: 03-2003
DOI: 10.1046/J.1432-1033.2003.03445.X
Abstract: To sustain life mammals have an absolute and continual requirement for oxygen, which is necessary to produce energy for normal cell survival and growth. Hence, maintaining oxygen homeostasis is a critical requirement and mammals have evolved a wide range of cellular and physiological responses to adapt to changes in oxygen availability. In the past few years it has become evident that the transcriptional protein complex hypoxia-inducible factor (HIF) is a key regulator of these processes. In this review we will focus on the way oxygen availability regulates HIF proteins and in particular we will discuss the way oxygen-dependent hydroxylation of specific amino acid residues has been demonstrated to regulate HIF function at the level of both protein stability and transcriptional potency.
No related grants have been discovered for Daniel Peet.