title: Cloning, characterization, and gene expression analysis of a novel cadmium metallothionein gene in Tetrahymena pigmentosa.
abstract: A novel cadmium-inducible metallothionein (MT) gene (Tpig-MT1) was cloned and sequenced from the ciliate Tetrahymena pigmentosa. The number of deduced amino acids is 118. The polypeptide possesses CCC and CC clusters characteristic of typical Tetrahymena Cd-inducible MTs. The structure of Tpig-MT1 is different from the reported Cd-MT in T. pyriformis, T. thermophila and T. pigmentosa. Tpig-MT1 contains two intragenic tandem repeats with 72.9% identity described as Tpig-MT1 (repeat A1) and Tpig-MT1 (repeat A2). The transcriptional response of Tpig-MT1 gene to different heavy metals (Cd, Cu, Zn, Hg, Pb) and oxidative stress (H(2)O(2)) was measured using real-time quantitative PCR. The results showed that the gene was quickly induced (1 h) by the five heavy metals and the order of expression level was Hg>Pb>Cd>Cu>Zn. The induction effect of H(2)O(2) was 5-fold after about 15 min, but soon decreased to a non-significant level (30 min). The genetic diversity of Tetrahymena MT genes is discussed in relation to the unique structure of the Tpig-MT1 gene and other reported Cd-MT isoforms.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.
authors.forename: Lina
authors.initials: L
authors.lastname: Guo
authors.forename: Chengjie
authors.initials: C
authors.lastname: Fu
authors.forename: Wei
authors.initials: W
authors.lastname: Miao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D017125:Genes, Protozoan; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008668:Metallothionein / Q000235:genetics*; D019216:Metals, Heavy / Q000494:pharmacology; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010802:Phylogeny; D015800:Protozoan Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D020080:Tandem Repeat Sequences; D013768:Tetrahymena / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D016054:DNA, Protozoan; D019216:Metals, Heavy; D015800:Protozoan Proteins; C004203:cadmium-binding protein; D008668:Metallothionein; D006861:Hydrogen Peroxide