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Mol Cell Biol. 1988 October; 8(10): 4469-4476

Structure of the rainbow trout metallothionein B gene and characterization of its metal-responsive region.

Department of Biological Sciences, University of Calgary, Alberta, Canada.

ABSTRACT

The trout metallothionein (MT) genes consist of two members. We describe the structure of the first fish MT (tMT-B) gene which shows an overall resemblance but some remarkable differences with mammalian MT genes. The similarities included (i) tripartite structure of the gene, (ii) conservation of cysteine residues, and (iii) a TATAAA signal and two copies of metal-responsive elements (MREs). The differences consisted of (i) an AT-rich tMT-B promoter compared with highly GC-rich mammalian MT promoters and (ii) a lack of SP1-binding sites in the tMT-B promoter. Functional analysis of the tMT-B 5'-flanking region following fusion with the bacterial chloramphenicol acetyltransferase gene and its transfection into the rainbow trout hepatoma cell line revealed that sequences from positions -600 to +8 are sufficient for regulation by metals. Further deletion analyses of this fragment suggested that a minimum of 100 nucleotides upstream of the transcription initiation site are required for induction by cadmium and zinc. The tMT-B promoter was also functional in the human hepatoblastoma cell line, suggesting that an MT regulatory factor(s) is conserved in phylogenetically distant species like humans and fish.

This article has been cited by other articles:

• Samson, S. L.-A., Gedamu, L. (1995). Metal-responsive Elements of the Rainbow Trout Metallothionein-B Gene Function for Basal and Metal-induced Activity. J. Biol. Chem. 270: 6864-6871 [Abstract] [Full Text]