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Abstract
The functions, purposes, and roles of metallothioneins have been the subject of speculations since the discovery of the protein over 60 years ago. This article guides through the history of investigations and resolves multiple contentions by providing new interpretations of the structure-stability-function relationship. It challenges the dogma that the biologically relevant structure of the mammalian proteins is only the one determined by X-ray diffraction and NMR spectroscopy. The terms metallothionein and thionein are ambiguous and insufficient to understand biological function. The proteins need to be seen in their biological context, which limits and defines the chemistry possible. They exist in multiple forms with different degrees of metalation and types of metal ions. The homoleptic thiolate coordination of mammalian metallothioneins is important for their molecular mechanism. It endows the proteins with redox activity and a specific pH dependence of their metal affinities. The proteins, therefore, also exist in different redox states of the sulfur donor ligands. Their coordination dynamics allows a vast conformational landscape for interactions with other proteins and ligands. Many fundamental signal transduction pathways regulate the expression of the dozen of human metallothionein genes. Recent advances in understanding the control of cellular zinc and copper homeostasis are the foundation for suggesting that mammalian metallothioneins provide a highly dynamic, regulated, and uniquely biological metal buffer to control the availability, fluctuations, and signaling transients of the most competitive Zn(II) and Cu(I) ions in cellular space and time.
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Affiliation(s)
- Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław 50-383, Poland
| | - Wolfgang Maret
- Departments of Biochemistry and Nutritional Sciences, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London SE1 9NH, U.K
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Okita Y, Rcom-H'cheo-Gauthier AN, Goulding M, Chung RS, Faller P, Pountney DL. Metallothionein, Copper and Alpha-Synuclein in Alpha-Synucleinopathies. Front Neurosci 2017; 11:114. [PMID: 28420950 PMCID: PMC5380005 DOI: 10.3389/fnins.2017.00114] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 02/22/2017] [Indexed: 12/14/2022] Open
Abstract
Metallothioneins (MTs) are proteins that function by metal exchange to regulate the bioavailability of metals, such as zinc and copper. Copper functions in the brain to regulate mitochondria, neurotransmitter production, and cell signaling. Inappropriate copper binding can result in loss of protein function and Cu(I)/(II) redox cycling can generate reactive oxygen species. Copper accumulates in the brain with aging and has been shown to bind alpha-synuclein and initiate its aggregation, the primary aetiological factor in Parkinson's disease (PD), and other alpha-synucleinopathies. In PD, total tissue copper is decreased, including neuromelanin-bound copper and there is a reduction in copper transporter CTR-1. Conversely cerebrospinal fluid (CSF) copper is increased. MT-1/2 expression is increased in activated astrocytes in alpha-synucleinopathies, yet expression of the neuronal MT-3 isoform may be reduced. MTs have been implicated in inflammatory states to perform one-way exchange of copper, releasing free zinc and recent studies have found copper bound to alpha-synuclein is transferred to the MT-3 isoform in vitro and MT-3 is found bound to pathological alpha-synuclein aggregates in the alpha-synucleinopathy, multiple systems atrophy. Moreover, both MT and alpha-synuclein can be released and taken up by neural cells via specific receptors and so may interact both intra- and extra-cellularly. Here, we critically review the role of MTs in copper dyshomeostasis and alpha-synuclein aggregation, and their potential as biomarkers and therapeutic targets.
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Affiliation(s)
- Yuho Okita
- Menzies Health Institute Queensland, Griffith UniversityGold Coast, QLD, Australia
| | | | - Michael Goulding
- Menzies Health Institute Queensland, Griffith UniversityGold Coast, QLD, Australia
| | - Roger S Chung
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie UniversitySydney, NSW, Australia
| | - Peter Faller
- Centre National de la Recherche Scientifique, Institut de Chimie UMR 7177, Université de StrasbourgStrasbourg, France.,University of Strasbourg Institute for Advanced StudyStrasbourg, France
| | - Dean L Pountney
- Menzies Health Institute Queensland, Griffith UniversityGold Coast, QLD, Australia
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Chen WY, Cheng YH, Hsieh NH, Wu BC, Chou WC, Ho CC, Chen JK, Liao CM, Lin P. Physiologically based pharmacokinetic modeling of zinc oxide nanoparticles and zinc nitrate in mice. Int J Nanomedicine 2015; 10:6277-92. [PMID: 26491297 PMCID: PMC4599717 DOI: 10.2147/ijn.s86785] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Zinc oxide nanoparticles (ZnO NPs) have been widely used in consumer products, therapeutic agents, and drug delivery systems. However, the fate and behavior of ZnO NPs in living organisms are not well described. The purpose of this study was to develop a physiologically based pharmacokinetic model to describe the dynamic interactions of 65ZnO NPs in mice. We estimated key physicochemical parameters of partition coefficients and excretion or elimination rates, based on our previously published data quantifying the biodistributions of 10 nm and 71 nm 65ZnO NPs and zinc nitrate (65Zn(NO3)2) in various mice tissues. The time-dependent partition coefficients and excretion or elimination rates were used to construct our physiologically based pharmacokinetic model. In general, tissue partition coefficients of 65ZnO NPs were greater than those of 65Zn(NO3)2, particularly the lung partition coefficient of 10 nm 65ZnO NPs. Sensitivity analysis revealed that 71 nm 65ZnO NPs and 65Zn(NO3)2 were sensitive to excretion and elimination rates in the liver and gastrointestinal tract. Although the partition coefficient of the brain was relative low, it increased time-dependently for 65ZnO NPs and 65Zn(NO3)2. The simulation of 65Zn(NO3)2 was well fitted with the experimental data. However, replacing partition coefficients of 65ZnO NPs with those of 65Zn(NO3)2 after day 7 greatly improved the fitness of simulation, suggesting that ZnO NPs might decompose to zinc ion after day 7. In this study, we successfully established a potentially predictive dynamic model for slowly decomposed NPs. More caution is suggested for exposure to 65ZnO NPs <10 nm because those small 65ZnO NPs tend to accumulate in the body for a relatively longer time than 71 nm 65ZnO NPs and 65Zn(NO3)2 do.
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Affiliation(s)
- Wei-Yu Chen
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yi-Hsien Cheng
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan
| | - Nan-Hung Hsieh
- Institute of Labor, Occupational Safety and Health, Ministry of Labor, New Taipei City, Taiwan
| | - Bo-Chun Wu
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan
| | - Wei-Chun Chou
- National Institute of Environmental Health Sciences, National Health Research Institutes, Zhunan, Taiwan
| | - Chia-Chi Ho
- National Institute of Environmental Health Sciences, National Health Research Institutes, Zhunan, Taiwan
| | - Jen-Kun Chen
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Zhunan, Taiwan
| | - Chung-Min Liao
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, Taiwan
| | - Pinpin Lin
- National Institute of Environmental Health Sciences, National Health Research Institutes, Zhunan, Taiwan
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Abstract
The Mediterranean marine sponge Crambe crambe is the source of two families of guanidine alkaloids known as crambescins and crambescidins. Some of the biological effects of crambescidins have been previously reported while crambescins have undergone little study. Taking this into account, we performed comparative transcriptome analysis to examine the effect of crambescin-C1 (CC1) on human tumor hepatocarcinoma cells HepG2 followed by validation experiments to confirm its predicted biological activities. We report herein that, while crambescin-A1 has a minor effect on these cells, CC1 protects them against oxidative injury by means of metallothionein induction even at low concentrations. Additionally, at high doses, CC1 arrests the HepG2 cell cycle in G0/G1 and thus inhibits tumor cell proliferation. The findings presented here provide the first detailed approach regarding the different effects of crambescins on tumor cells and provide a basis for future studies on other possible cellular mechanisms related to these bioactivities.
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Reed S, Qin X, Ran-Ressler R, Brenna JT, Glahn RP, Tako E. Dietary zinc deficiency affects blood linoleic acid: dihomo-γ-linolenic acid (LA:DGLA) ratio; a sensitive physiological marker of zinc status in vivo (Gallus gallus). Nutrients 2014; 6:1164-80. [PMID: 24658588 PMCID: PMC3967184 DOI: 10.3390/nu6031164] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 03/01/2014] [Accepted: 03/05/2014] [Indexed: 01/09/2023] Open
Abstract
Zinc is a vital micronutrient used for over 300 enzymatic reactions and multiple biochemical and structural processes in the body. To date, sensitive and specific biological markers of zinc status are still needed. The aim of this study was to evaluate Gallus gallus as an in vivo model in the context of assessing the sensitivity of a previously unexplored potential zinc biomarker, the erythrocyte linoleic acid: dihomo-γ-linolenic acid (LA:DGLA) ratio. Diets identical in composition were formulated and two groups of birds (n = 12) were randomly separated upon hatching into two diets, Zn(+) (zinc adequate control, 42.3 μg/g zinc), and Zn(−) (zinc deficient, 2.5 μg/g zinc). Dietary zinc intake, body weight, serum zinc, and the erythrocyte fatty acid profile were measured weekly. At the conclusion of the study, tissues were collected for gene expression analysis. Body weight, feed consumption, zinc intake, and serum zinc were higher in the Zn(+) control versus Zn(−) group (p < 0.05). Hepatic TNF-α, IL-1β, and IL-6 gene expression were higher in the Zn(+) control group (p < 0.05), and hepatic Δ6 desaturase was significantly higher in the Zn(+) group (p < 0.001). The LA:DGLA ratio was significantly elevated in the Zn(−) group compared to the Zn(+) group (22.6 ± 0.5 and 18.5 ± 0.5, % w/w, respectively, p < 0.001). This study suggests erythrocyte LA:DGLA is able to differentiate zinc status between zinc adequate and zinc deficient birds, and may be a sensitive biomarker to assess dietary zinc manipulation.
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Affiliation(s)
- Spenser Reed
- USDA-ARS, Robert Holley Center for Agriculture & Health, Ithaca, NY 14853, USA.
| | - Xia Qin
- Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
| | - Rinat Ran-Ressler
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
| | - James Thomas Brenna
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
| | - Raymond P Glahn
- USDA-ARS, Robert Holley Center for Agriculture & Health, Ithaca, NY 14853, USA.
| | - Elad Tako
- USDA-ARS, Robert Holley Center for Agriculture & Health, Ithaca, NY 14853, USA.
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Albrecht EA, Dhanasekaran SM, Tomlins S. Immediate early inflammatory gene responses of human umbilical vein endothelial cells to hemorrhagic venom. Inflamm Res 2010; 60:213-7. [PMID: 21153857 DOI: 10.1007/s00011-010-0286-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 10/25/2010] [Accepted: 11/22/2010] [Indexed: 01/23/2023] Open
Abstract
OBJECTIVE AND DESIGN This report describes a focused immediate early gene response by human umbilical vein endothelial cells (HUVEC) to Echis carinatus snake venom. MATERIALS OR SUBJECTS Primary cultures of HUVEC were used to assess acute inflammatory gene responses. TREATMENTS Crude E. carinatus venom (2.5 µg/ml) was used to stimulate HUVEC. RESULTS HUVEC stimulated for 3 h with E. carinatus venom showed a focused response to the venom, with significant increases in metallothionein (e.g., MT1H, MT2A, MT1X) and cytochrome P450 (e.g., CYP1A1, CYP1B1) gene expressions compared to non-stimulated controls. Several other genes involved in cell growth and matrix attachment were repressed [e.g., thrombospondin 1 (THBS1), connective tissue growth factor (CTGF)]. CONCLUSIONS These data suggest that acute vascular injury induced by hemorrhagic snake venom initiates an anti-oxidant response primarily involving metallothioneins.
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Affiliation(s)
- Eric A Albrecht
- Department of Biology and Physics, Kennesaw State University, 1000 Chastain Rd. Bldg 12 Rm 308, Kennesaw, GA 30144, USA.
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Scheckhuber CQ, Grief J, Boilan E, Luce K, Debacq-Chainiaux F, Rittmeyer C, Gredilla R, Kolbesen BO, Toussaint O, Osiewacz HD. Age-related cellular copper dynamics in the fungal ageing model Podospora anserina and in ageing human fibroblasts. PLoS One 2009; 4:e4919. [PMID: 19305496 PMCID: PMC2654708 DOI: 10.1371/journal.pone.0004919] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 02/11/2009] [Indexed: 12/14/2022] Open
Abstract
In previous investigations an impact of cellular copper homeostasis on ageing of the ascomycete Podospora anserina has been demonstrated. Here we provide new data indicating that mitochondria play a major role in this process. Determination of copper in the cytosolic fraction using total reflection X-ray fluorescence spectroscopy analysis and eGfp reporter gene studies indicate an age-related increase of cytosolic copper levels. We show that components of the mitochondrial matrix (i.e. eGFP targeted to mitochondria) become released from the organelle during ageing. Decreasing the accessibility of mitochondrial copper in P. anserina via targeting a copper metallothionein to the mitochondrial matrix was found to result in a switch from a copper-dependent cytochrome-c oxidase to a copper-independent alternative oxidase type of respiration and results in lifespan extension. In addition, we demonstrate that increased copper concentrations in the culture medium lead to the appearance of senescence biomarkers in human diploid fibroblasts (HDFs). Significantly, expression of copper-regulated genes is induced during in vitro ageing in medium devoid of excess copper suggesting that cytosolic copper levels also increase during senescence of HDFs. These data suggest that the identified molecular pathway of age-dependent copper dynamics may not be restricted to P. anserina but may be conserved from lower eukaryotes to humans.
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Affiliation(s)
- Christian Q. Scheckhuber
- Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Jürgen Grief
- Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Emmanuelle Boilan
- Research Unit on Cellular Biology, University of Namur, Namur, Belgium
| | - Karin Luce
- Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | | | - Claudia Rittmeyer
- Institute of Inorganic Chemistry/Analytical Chemistry, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Ricardo Gredilla
- Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Bernd O. Kolbesen
- Institute of Inorganic Chemistry/Analytical Chemistry, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
| | - Olivier Toussaint
- Research Unit on Cellular Biology, University of Namur, Namur, Belgium
| | - Heinz D. Osiewacz
- Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
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Tang CM, Westling J, Seto E. trans repression of the human metallothionein IIA gene promoter by PZ120, a novel 120-kilodalton zinc finger protein. Mol Cell Biol 1999; 19:680-9. [PMID: 9858591 PMCID: PMC83925 DOI: 10.1128/mcb.19.1.680] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Metallothioneins are small, highly conserved, cysteine-rich proteins that bind a variety of metal ions. They are found in virtually all eukaryotic organisms and are regulated primarily at the transcriptional level. In humans, the predominant metallothionein gene is hMTIIA, which accounts for 50% of all metallothioneins expressed in cultured human cells. The hMTIIA promoter is quite complex. In addition to cis-acting DNA sequences that serve as binding sites for trans-acting factors such as Sp1, AP1, AP2, AP4, and the glucocorticoid receptor, the hMTIIA promoter contains eight consensus metal response element sequences. We report here the cloning of a novel zinc finger protein with a molecular mass of 120 kDa (PZ120) that interacts specifically with the hMTIIA transcription initiation site. The PZ120 protein is ubiquitously expressed in most tissues and possesses a conserved poxvirus and zinc finger (POZ) motif previously found in several zinc finger transcription factors. Intriguingly, we found that a region of PZ120 outside of the zinc finger domain can bind specifically to the hMTIIA DNA. Using transient-transfection analysis, we found that PZ120 repressed transcription of the hMTIIA promoter. These results suggest that the hMTIIA gene is regulated by an additional negative regulator that has not been previously described.
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Affiliation(s)
- C M Tang
- H. Lee Moffitt Cancer Center and Research Institute, Department of Medical Microbiology, College of Medicine, University of South Florida, Tampa, Florida 33612, USA
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Vasconcelos MH, Tam SC, Beattie JH, Hesketh JE. Evidence for differences in the post-transcriptional regulation of rat metallothionein isoforms. Biochem J 1996; 315 ( Pt 2):665-71. [PMID: 8615845 PMCID: PMC1217248 DOI: 10.1042/bj3150665] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The expression of metallothionein (MT)-1 and -2 mRNAs in rat liver following administration of Cd or Cu was investigated using specific oligonucleotides. The specificity was confirmed using a competitive prehybridization assay. Cd injection caused a biphasic induction of both isoform mRNAs, whereas Cu induced a sustained, monophasic response. Analysis of polyribosomal RNA showed that, after both Cd and Cu treatments, the recruitment of MT-1 mRNA into polyribosomes paralleled the increase in transcription, but the increase of polyribosomal MT-2 mRNA was less than that of total MT-2 mRNA. This indicates that not all the MT-2 mRNA induced was translated, suggesting that there is translational control of MT-2 mRNA expression, but not of MT-1 mRNA. This hypothesis was supported by the observation that, after Cu treatment, the induction of MT-1 protein was induced to the same extent as MT-1 mRNA, whereas the total MT protein (MT-1 + MT-2) was increased far less (7-fold) than MT-2 mRNA (30-fold).
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Affiliation(s)
- M H Vasconcelos
- Division of Biochemical Sciences, Rowett Research Institute, Aberdeen, Scotland, U.K
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Czupryn M, Brown WE, Vallee BL. Zinc rapidly induces a metal response element-binding factor. Proc Natl Acad Sci U S A 1992; 89:10395-9. [PMID: 1332048 PMCID: PMC50345 DOI: 10.1073/pnas.89.21.10395] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Metal activation of metallothionein gene transcription is mediated by specific promoter sequences, termed metal regulatory elements (MREs). Nuclear extracts prepared from various human cell lines were assayed for their capacity to bind to a synthetic human MREa (hMREa) oligomer. Electrophoretic mobility-shift assays with extracts from control cells detected a single hMREa-containing complex. Addition to the growth medium of zinc, cadmium, or copper--metals known to induce MT biosynthesis in vivo--resulted in the rapid but reversible appearance of a second distinct hMREa-protein complex in all cell lines studied. This result was not seen when the metals were added directly to the extracts from control cells. DNA-binding protein blotting, UV crosslinking, and electroelution experiments were used to characterize the two hMREa-binding factors, termed BF1 and BF2. MRE-BF1 has an apparent molecular mass of approximately 86 kDa and binds to the hMREa in control cells, whereas MRE-BF2 consists of two molecules of approximately 28 kDa and binds to the hMREa in metal-treated cells. EDTA and o-phenanthroline inhibited binding of both factors to hMREa in a dose-dependent manner, indicating that a metal atom or atoms are essential for interaction of the factors with DNA.
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Affiliation(s)
- M Czupryn
- Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, Boston, MA 02115
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Abundance of hepatic metallothionein mRNA is increased by protein-synthesis inhibitors. Evidence for transcriptional activation and post-transcriptional regulation. Biochem J 1991; 273(Pt 1):185-8. [PMID: 1989579 PMCID: PMC1150213 DOI: 10.1042/bj2730185] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ongoing protein synthesis is a prerequisite in the expression of some genes. We studied the effect of various protein synthesis inhibitors on the expression of the avian metallothionein (MT) gene. Chicken embryonic hepatocytes in culture were exposed to various concentrations of cycloheximide, puromycin and pactamycin. At concentrations which decreased total protein synthesis by about 90% each inhibitor increased MT mRNA accumulation approx. 5-fold at 9 h of incubation. Incubation with puromycin or zinc for 2 h markedly increased the rate of MT gene transcription. Estimates of the half-life of MT mRNA by using actinomycin D suggested for cycloheximide, but not puromycin, decreased the decay rate of MT mRNA. These data suggest the potential for post-transcriptional regulation of the avian MT gene. We conclude that different antibiotics increase the accumulation of hepatocyte MT mRNA by different mechanisms and that the possibility of multiple mechanisms should be considered in other studies of the role of protein synthesis in gene expression.
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