Gene structure and expression of metallothionein during metal exposures in Hemibarbus mylodon

Metallothionein gene was characterized in Hemibarbus mylodon, an endangered fish species. H. mylodon NIT shared a high homology with other vertebrate MTs, including (1) tripartite exon/intron structure, (2) typical regulatory elements such as MREs and GC boxes in the 5'-flanking region, and (3) high proportion of Cysteines (33.3%) in its amino acid sequence. NIT mRNA was ubiquitously detected in various tissues. Basal level of NIT mRNA was the highest in ovary while the lowest in heart. Transcription of MT was highly inducible by exposures to waterborne cadmium (0.1-10 mu M), copper (2-10 mu M) or zinc (2-10 mu M), based on real-time RT-PCR. Cadmium was more potent for the stimulation of NIT transcripts than copper and zinc. Liver was more responsive to heavy metals than kidney and gill. In overall, the transcriptional activation of NIT gene by metal exposures followed a dose- and/or time-dependent fashion. (C) 2007 Elsevier Inc. All rights reserved.