Sequence homology of Chinese hamster metallothionein genes I and II to those of the mouse and rat, and their amplification in Cd-resistant cells

Characterisation of DNA probes for the analysis of metallothionein gene expression in the bank vole (Clethrionomys glareolus)

DNA probes have been developed for subsequent use in monitoring the exposure of animals to heavy metal pollution in terrestrial environments using metallothionein (MT) gene expression in the bank vole (Clethrionomys glareolus). Three different bank vole sequences were characterised corresponding to the cDNA and the genomic DNA for MT-I and the genomic DNA for MT-II. Nucleotide sequence analysis indicates that the coding sequences of the bank vole MT-I and MT-II genes exhibit a very high degree of similarity (greater than 92%) to the corresponding genes of the Chinese hamster, the mouse and the rat. In common with other mammalian MT genes, both the MT-I and MT-II genes in the bank vole are interrupted by two introns, which are at identical positions as those in other rodent MT genes; furthermore, the sizes of these introns are similar to those in other rodents with the first intron being larger than the second and those in the MT-I gene being larger than those in the MT-II gene. The predicted amino acid sequence for the proteins shows that both proteins contain 20 cysteine residues at positions identical to those in other known mammalian MTs. The availability of these DNA sequences now provides a good opportunity to investigate MT gene expression and possible gene amplification in bank voles exposed to metal pollution.

Metallothionein cDNA, promoter, and genomic sequences of the tropical green mussel, Perna viridis

The primary structure of the cDNA and metallothionein (MT) genomic sequences of the tropical green mussel (Perna viridis) was determined. The complete cDNA sequences were obtained using degenerate primers designed from known metallothionein consensus amino acid sequences from the temperate species Mytilus edulis. The amino acid sequences of P. viridis metallothionein deduced from the coding region consisted of 72 amino acids with 21 cysteine residues and 9 Cys-X-Cys motifs corresponding to Type I MT class of other species. Two different genomic sequences coding for the same mRNA were obtained. Each putative gene contained a unique 5'UTR and two unique introns located at the same splice sites. The promoters for both genes were different in length and both contained metal responsive elements and active protein-binding sites. The structures of the genomic clones were compared with those of other species. J. Exp. Zool. 284:445-453, 1999.

The genetic effects of environmental lead

This article reviews the effects of lead on genetic systems in the context of lead's various other toxic effects and its abundance and distribution in the environment. Lead is perhaps the longest used and best recognized toxic environmental chemical, yet it continued be used recklessly until only very recently. Lead is thus a lesson in the limitations and strengths of science, human conscience and common sense. Lead has been tested and found to be capable of eliciting a positive response in an extraordinarily wide range of biological and biochemical tests; among them tests for enzyme inhibition, fidelity of DNA synthesis, mutation, chromosome aberrations, cancer and birth defects. It reacts or complexes with many biomolecules and adversely affects the reproductive, nervous, gastrointestinal, immune, renal, cardiovascular, skeletal, muscular and hematopoietic systems as well as developmental processes. It is likely that lead is a selective agent that continues to act on and influence the genetic structure and future evolution of exposed plant and animal populations.