MT Genes (mt + gene)

Distribution by Scientific Domains


Selected Abstracts


Comparative metal binding and genomic analysis of the avian (chicken) and mammalian metallothionein

FEBS JOURNAL, Issue 3 2006
Laura Villarreal
Chicken metallothionein (ckMT) is the paradigm for the study of metallothioneins (MTs) in the Aves class of vertebrates. Available literature data depict ckMT as a one-copy gene, encoding an MT protein highly similar to mammalian MT1. In contrast, the MT system in mammals consists of a four-member family exhibiting functional differentiation. This scenario prompted us to analyse the apparently distinct evolutionary patterns followed by MTs in birds and mammals, at both the functional and structural levels. Thus, in this work, the ckMT metal binding abilities towards Zn(II), Cd(II) and Cu(I) have been thoroughly revisited and then compared with those of the mammalian MT1 and MT4 isoforms, identified as zinc- and copper-thioneins, respectively. Interestingly, a new mechanism of MT dimerization is reported, on the basis of the coordinating capacity of the ckMT C-terminal histidine. Furthermore, an evolutionary study has been performed by means of in silico analyses of avian MT genes and proteins. The joint consideration of the functional and genomic data obtained questions the two features until now defining the avian MT system. Overall, in vivo and in vitro metal-binding results reveal that the Zn(II), Cd(II) and Cu(I) binding abilities of ckMT lay between those of mammalian MT1 and MT4, being closer to those of MT1 for the divalent metal ions but more similar to those of MT4 for Cu(I). This is consistent with a strong functional constraint operating on low-copy number genes that must cope with differentiating functional limitation. Finally, a second MT gene has been identified in silico in the chicken genome, ckMT2, exhibiting all the features to be considered an active coding region. The results presented here allow a new insight into the metal binding abilities of warm blooded vertebrate MTs and their evolutionary relationships. [source]


Structural and bioinformatic analysis of the Roman snail Cd-Metallothionein gene uncovers molecular adaptation towards plasticity in coping with multifarious environmental stress

MOLECULAR ECOLOGY, Issue 11 2009
MARGIT EGG
Abstract Metallothioneins (MTs) are a family of multifunctional proteins involved, among others, in stress response. The Cadmium (Cd)-MT gene of the Roman snail (Helix pomatia), for example, encodes for a protein induced upon cadmium exposure. While our previous studies have demonstrated that the expressed Cd-MT isoform of Roman snails assists detoxification of cadmium, the present work focuses on the potential plasticity of this gene in response to a variety of environmental stressors playing a crucial role in the specific ecological niche of H. pomatia. Our hypothesis is based on a bioinformatic approach involving gene sequencing, structural and in silico analysis of transcription factor binding sites (TFBs), and a comparison of these features with other MT genes. Our results show that the Roman snail's Cd-MT gene not only is the largest known MT gene, but also contains , apart from the regulatory promoter region , several intronic repeat cassettes of putative TFBs suggested to be involved in environmental stress response, immune competence, and regulation of gene expression. Moreover, intronic scaffold/matrix attachment regions (S/MARs) and stress-induced duplex destabilization sites confer a high potential for epigenetic gene regulation. This suggested regulatory plasticity is also supported by physiological data showing that Cd-MT in Roman snails can be induced differentially not only after cadmium exposure, but also in response to nonmetallic environmental stressors. It is concluded that structural analysis combined with bioinformatic screening may constitute valuable tools for predicting the potential for plasticity and niche-specific adaptation of stress-responsive genes in populations living under rapidly changing environmental conditions. [source]


Comparative metal binding and genomic analysis of the avian (chicken) and mammalian metallothionein

FEBS JOURNAL, Issue 3 2006
Laura Villarreal
Chicken metallothionein (ckMT) is the paradigm for the study of metallothioneins (MTs) in the Aves class of vertebrates. Available literature data depict ckMT as a one-copy gene, encoding an MT protein highly similar to mammalian MT1. In contrast, the MT system in mammals consists of a four-member family exhibiting functional differentiation. This scenario prompted us to analyse the apparently distinct evolutionary patterns followed by MTs in birds and mammals, at both the functional and structural levels. Thus, in this work, the ckMT metal binding abilities towards Zn(II), Cd(II) and Cu(I) have been thoroughly revisited and then compared with those of the mammalian MT1 and MT4 isoforms, identified as zinc- and copper-thioneins, respectively. Interestingly, a new mechanism of MT dimerization is reported, on the basis of the coordinating capacity of the ckMT C-terminal histidine. Furthermore, an evolutionary study has been performed by means of in silico analyses of avian MT genes and proteins. The joint consideration of the functional and genomic data obtained questions the two features until now defining the avian MT system. Overall, in vivo and in vitro metal-binding results reveal that the Zn(II), Cd(II) and Cu(I) binding abilities of ckMT lay between those of mammalian MT1 and MT4, being closer to those of MT1 for the divalent metal ions but more similar to those of MT4 for Cu(I). This is consistent with a strong functional constraint operating on low-copy number genes that must cope with differentiating functional limitation. Finally, a second MT gene has been identified in silico in the chicken genome, ckMT2, exhibiting all the features to be considered an active coding region. The results presented here allow a new insight into the metal binding abilities of warm blooded vertebrate MTs and their evolutionary relationships. [source]


Investigation of Protective Reactions Against Cadmium Toxicity in the Cells Established from a Transgenic Mouse Deficient in the Metallothionein Genes

JOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 2 2003
Tetsuya Abe
Objective:, To characterize a fibroblast cell strain which we established from an metallothionein (MT) knock-out (KO) mouse and to determine whether expression of the Hsp genes induced by cadmium is related to expression of the MT-I and -II genes. Methods:, We established a fibroblast cell strain (named "MT-KO2") derived from the peritoneum of an MT-KO mouse which is deficient in the MT-I and -II genes. We determined an expression of MT-I, Hsp32 and Grp 78 genes by Northern blot analysis. Results:, The mRNA level of MT-I, an isoform of the MT gene products, was induced dose-dependently in responce to increasing concentrations of CdCl2 (5,25 ÁM) in a fibroblast cell strain derived from the peritoneum of an MT wild type mouse (named "MT-W3"). But it was not induced in MT-KO2 cells after the same treatment. There was no significant difference between MT-KO2 and MT-W3 cells in a concentration of intracellular glutathione (reduced form) under normal conditions. MT-KO2 cells were not more sensitive to cytotoxicity of CdCl2 than in MT-W3 cells. Expression of the Hsp32 gene was more extensively enhanced in MT-KO2 cells than in MT-W3 cells after treatment with 5,10 ÁM CdCl2 for 5 hours. Furthermore, the cellular concentration of reduced glatathione (GSH) was also more increased in MT-KO2 cells than in MT-W3 cells after treatment with 50 ÁM CdCl2 for 3 hours. Conclusions:, Expression of the Hsp32 gene tends to be increased in MT-KO2 cells in response to cadmium exposure. The expression of the Hsp32 gene and increase in the cellular concentration of GSH may be augmented to compensate for the impaired expression of the MT genes in MT-KO2 cells. [source]


Structural and bioinformatic analysis of the Roman snail Cd-Metallothionein gene uncovers molecular adaptation towards plasticity in coping with multifarious environmental stress

MOLECULAR ECOLOGY, Issue 11 2009
MARGIT EGG
Abstract Metallothioneins (MTs) are a family of multifunctional proteins involved, among others, in stress response. The Cadmium (Cd)-MT gene of the Roman snail (Helix pomatia), for example, encodes for a protein induced upon cadmium exposure. While our previous studies have demonstrated that the expressed Cd-MT isoform of Roman snails assists detoxification of cadmium, the present work focuses on the potential plasticity of this gene in response to a variety of environmental stressors playing a crucial role in the specific ecological niche of H. pomatia. Our hypothesis is based on a bioinformatic approach involving gene sequencing, structural and in silico analysis of transcription factor binding sites (TFBs), and a comparison of these features with other MT genes. Our results show that the Roman snail's Cd-MT gene not only is the largest known MT gene, but also contains , apart from the regulatory promoter region , several intronic repeat cassettes of putative TFBs suggested to be involved in environmental stress response, immune competence, and regulation of gene expression. Moreover, intronic scaffold/matrix attachment regions (S/MARs) and stress-induced duplex destabilization sites confer a high potential for epigenetic gene regulation. This suggested regulatory plasticity is also supported by physiological data showing that Cd-MT in Roman snails can be induced differentially not only after cadmium exposure, but also in response to nonmetallic environmental stressors. It is concluded that structural analysis combined with bioinformatic screening may constitute valuable tools for predicting the potential for plasticity and niche-specific adaptation of stress-responsive genes in populations living under rapidly changing environmental conditions. [source]


Characterization of the Arabidopsis metallothionein gene family: tissue-specific expression and induction during senescence and in response to copper

NEW PHYTOLOGIST, Issue 2 2003
Woei-Jiun Guo
Summary ,Expression and regulation of Arabidopsis metallothionein (MT) genes were investigated to examine the functions of MTs in plants. ,To examine the tissue-specific expression of MT genes, GUS reporter gene activity driven by promoters of MT1a, MT2a, MT2b and MT3 was analysed in transgenic plants. ,MT1a and MT2b are expressed in the phloem of all organs and are copper (Cu)-inducible; MT2a and MT3, by contrast, are expressed predominantly in mesophyll cells and are also induced by Cu in young leaves and at root tips. Expression of MT genes is highly induced by Cu in trichomes and increases during senescence. Expression of MT4 genes is restricted to seeds. ,We propose that plant MTs have distinct functions in heavy metal homeostasis, especially for Cu: MT1a and MT2b are involved in the distribution of Cu via the phloem, while MT2a and MT3 chaperone excess metals in mesophyll cells and root tips. These functional capabilities may allow MTs to play a role in mobilization of metal ions from senescing leaves and the sequestration of excess metal ions in trichomes. [source]