Identification of a signal transducer and activator of transcription (STAT) binding site in the mouse metallothionein-I promoter involved in interleukin-6-induced gene expression.
TL;DR: The effects of LPS on hepatic MT-I gene expression are mediated by IL-6 and involve the activation of STAT-binding to the proximal promoter.
Abstract: Mechanisms of regulation of mouse metallothionein (MT)-I gene expression in response to bacterial endotoxin-lipopolysaccharide (LPS) were examined. Northern blot analysis of hepatic MT-I mRNA in interleukin (IL)-6 or tumour necrosis factor (TNF)-receptor type I knock-out mice demonstrated that IL-6, not TNF-alpha, is of central importance in mediating hepatic MT-I gene expression in vivo after LPS injection. In vivo genomic footprinting of the MT-I promoter demonstrated a rapid increase, after LPS injection, in the protection of several guanine residues in the -250 to -300 bp region of the MT-I promoter. The protected bases were within sequences which resemble binding sites for the signal transducers and activators of transcription (STAT) transcription factor family. Electrophoretic mobility-shift assays using oligonucleotides from footprinted MT-I promoter regions showed that injection of LPS resulted in a rapid increase in the specific, high-affinity, in vitro binding of STAT1 and STAT3 to a binding site at -297 bp (TTCTCGTAA). Western blotting of hepatic nuclear proteins showed that the time-course for changes of total nuclear STAT1 and STAT3 after LPS injection paralleled the increased complex formation in vitro using this oligonucleotide, and binding was specifically competed for by a functional STAT-binding site from the rat alpha2-macroglobulin promoter. Furthermore, the MT-I promoter -297 bp STAT-binding site conferred IL-6 responsiveness in the context of a minimal promoter in transient transfection assays using HepG2 cells. This study suggests that the effects of LPS on hepatic MT-I gene expression are mediated by IL-6 and involve the activation of STAT-binding to the proximal promoter.
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TL;DR: Understanding of the multi-faceted role of MT is enhanced by use of mice with altered gene expression, emphasised in this review.
Abstract: Metallothioneins (MTs) are intracellular, low molecular, low molecular weight, cysteine-rich proteins. Ubiquitous in eukaryotes, MTs have unique structural characteristics to give potent metal-binding and redox capabilities. A primary role has not been identified, and remains elusive, as further functions continue to be discovered. The most widely expressed isoforms in mammals, MT-1 and MT-2, are rapidly induced in the liver by a wide range of metals, drugs and inflammatory mediators. In teh gut and pancreas, MT responds mainly to Zn status. A brain isoform, MT-3, has a specific neuronal growth inhibitory activity, while MT-1 and MT-2 have more diverse functions related to their thiolate cluster structure. These include involvement in Zn homeostasis, protection against heavy metal (especially Cd) and oxidant damage, and metabolic regulation via Zn donation, sequestration and/or redox control. Use of mice with altered gene expression has enhance our understanding of the multifaceted role of MT, emphasised in this review.
1,228 citations
TL;DR: It is shown that STAT3 activation is much stronger and more prolonged in STAT1-null mouse embryo fibroblasts than in wild-type cells, suggesting that their relative abundance may vary substantially in different normal cell types, under different conditions or in tumors is likely to have a major impact on how cells behave in response to different cytokines.
307 citations
TL;DR: It is found that GM-CSF-activated infected macrophages sequestered labile Zn by inducing binding to metallothioneins (MTs) in a STAT3 and STAT5 transcription-factor-dependent manner, illuminating a GM- CSF-induced Zn-sequestration network that drives phagocyte antimicrobial effector function.
189 citations
Cites background from "Identification of a signal transduc..."
..., 2001) and STAT binding sites are present on the Mt promoter (Lee et al., 1999)....
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...GM-CSF signals through STAT5 (Bhattacharya et al., 2001) and STAT binding sites are present on the Mt promoter (Lee et al., 1999)....
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TL;DR: The properties and CNS expression of MT are briefly reviewed, and Dr Hidalgo describes his pioneering work using transgenic models of MT expression to demonstrate how this protein plays a major role in the defence of the CNS against neurodegenerative disorders and other CNS injuries.
Abstract: Metallothionein (MT) is an enigmatic protein, and its physiological role remains a matter of intense study and debate 50 years after its discovery. This is particularly true of its function in the central nervous system (CNS), where the challenge remains to link its known biochemical properties of metal binding and free radical scavenging to the intricate workings of brain. In this compilation of four reports, first delivered at the 11th International Neurotoxicology Association (INA-11) Meeting, June 2007, the authors present the work of their laboratories, each of which gives an important insight into the actions of MT in the brain. What emerges is that MT has the potential to contribute to a variety of processes, including neuroprotection, regeneration, and even cognitive functions. In this article, the properties and CNS expression of MT are briefly reviewed before Dr Hidalgo describes his pioneering work using transgenic models of MT expression to demonstrate how this protein plays a major role in the defence of the CNS against neurodegenerative disorders and other CNS injuries. His group's work leads to two further questions, what are the mechanisms at the cellular level by which MT acts, and does this protein influence higher order issues of architecture and cognition? These topics are addressed in the second and third sections of this review by Dr West, and Dr Levin and Dr Eddins, respectively. Finally, Dr Aschner examines the ability of MT to protect against a specific toxicant, methylmercury, in the CNS.
174 citations
Cites background from "Identification of a signal transduc..."
...…both cytokines regulate MT-I/II expression, which is in line with results obtained with transgenic mice overexpressing either IL-6 (Carrasco et al., 1999; Hernandez et al., 1997) or TNF-α (Carrasco et al., 2000a) and with the presence of STAT response elements in the promoters (Lee et al., 1999)....
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...Increased levels of MT-I/II in response to inflammatory factors is very likely to be influenced by cytokines such as interleukin (IL-6) through signal transducer and activator of transcription (STAT) factors (Lee et al., 1999)....
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...Increased levels of MT-I/II in response to inflammatory factors is very likely to be influenced by cytokines such as interleukin (IL-6) through signal transducer and activator of transcription (STAT) factors (Lee et al., 1999).....
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..., 2000a) and with the presence of STAT response elements in the promoters (Lee et al., 1999)....
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TL;DR: The rapid and robust induction of metallothioneins (MT)-I and II by a variety of inducers that include heavy toxic metals, reactive oxygen species, and different types of stress provide a useful system to study the molecular mechanisms of this unique induction process.
Abstract: The rapid and robust induction of metallothioneins (MT)-I and II by a variety of inducers that include heavy toxic metals, reactive oxygen species, and different types of stress provide a useful system to study the molecular mechanisms of this unique induction process. The specific expression of MT-III in the brain and of MT-IV in the squamous epithelium of skin and tongue offers a unique opportunity to identify and characterize the tissue-specific factors involved in their expression. Studies using transgenic mice that overexpress MTs or MT null mice have revealed the role of MT in the protection of cells against numerous tissue-damaging agents such as reactive oxygen species. The primary physiological function of these proteins, however, remains an enigma. Considerable advances have been made in the identification of the cis-acting elements that are involved in the constitutive and induced expression of MT-I and MT-II. By contrast, only one key trans-activating factor, namely MTF-1, has been extensively characterized. Studies on the epigenetic silencing of MT-I and MT-II by promoter hypermethylation in some cancer cells have posed interesting questions concerning the functional relevance of MT gene silencing, the molecular mechanisms of MT suppression in these cells, particularly chromatin modifications, and the characteristics of the repressors.
155 citations
References
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TL;DR: Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products.
Abstract: Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products. Four major components of the head are cleaved during the process of assembly, apparently after the precursor proteins have assembled into some large intermediate structure.
232,912 citations
TL;DR: The discovery of a STAT in Drosophila, and most recently in Dictyostelium discoideum, implies an ancient evolutionary origin for this dual-function set of proteins.
Abstract: STATs (signal transducers and activators of transcription) are a family of latent cytoplasmic proteins that are activated to participate in gene control when cells encounter various extracellular polypeptides. Biochemical and molecular genetic explorations have defined a single tyrosine phosphorylation site and, in a dimeric partner molecule, an Src homology 2 (SH2) phosphotyrosine-binding domain, a DNA interaction domain, and a number of protein-protein interaction domains (with receptors, other transcription factors, the transcription machinery, and perhaps a tyrosine phosphatase). Mouse genetics experiments have defined crucial roles for each known mammalian STAT. The discovery of a STAT in Drosophila , and most recently in Dictyostelium discoideum , implies an ancient evolutionary origin for this dual-function set of proteins.
3,860 citations
TL;DR: This review outlines the principal cellular and molecular mechanisms that control initiation of the tissue response at the site of injury, the recruitment of the systemic defense mechanisms, the acute phase response of the liver and the resolution of the acutephase response.
2,928 citations
TL;DR: Systemic reaction characterized by fever, leukocytosis, increase in erythrocyte sedimentation rate, increases in LeucocyTosis secretion of ACTH and glucocorticoids, and by dramatic changes in the concentration of some plasma ,l' proteins.
Abstract: systemic reaction characterized by fever, leukocytosis, increase in erythrocyte sedimentation rate, increases in Leucocytosis secretion of ACTH and glucocorticoids, activation of Complement activat complement and clotting cascades, decreases in serum levels of iron and zinc, a negative nitrogen balance, and by dramatic changes in the concentration of some plasma ,l' proteins. These proteins are named acute phase proteins. i
2,680 citations
TL;DR: This review will examine how two receptor associated tyrosine kinases from the JAK family mediate the transduction of signal directly from receptor to nucleus.
Abstract: Cytokines and growth factors regulate multiple aspects of cell growth through their interactions with specific receptors. These receptors initiate signals directed at both the cytoplasmic and the nuclear compartments. Many of the nuclear signals culminate in the induction of new genes. Characterization of the ability of IFN-alpha to rapidly induce new genes has led to the identification of a new signaling paradigm, the JAK-STAT (Signal Transducers and Activators of Transcription) pathway. In the IFN-alpha pathway, two receptor associated tyrosine kinases from the JAK family, Jak1 and Tyk2, mediate the activation of two latent cytoplasmic transcription factors, Stat1 and Stat2. More recent studies have not only determined that this pathway is used extensively, but have led to the identification of additional components (e.g., Jak2, Jak3, Stat3, Stat4, Stat5, and Stat6). This review will examine how these components mediate the transduction of signal directly from receptor to nucleus.
1,878 citations