Gene expression metal, effects

Cellular responses to metal ions include changes of patterns of gene expression. Many of these changes are non-specific shock effects for example, subsets of the heat shock proteins are synthesised in response to Cd (Czarnecka et al., 1984 Lin et al., 1984 Delhaize et al., 1989). However, some mRNAs are specifically induced by Cd (Delhaize et al., 1989). Thus, by examining metal-regulated gene expression, whether specific or non-specific, it may be possible to determine the relative roles of proteins and polypeptides specific to metal homeostasis and metal tolerance, as opposed to functions involved in general stress responses. 

Several systems have been established which can regulate gene expression. For instance, there are systems which rely on the addition of steroid hormones or heavy metal ions. However, certain physiologic or toxic effects may result and high basal-transcriptional activity may limit their usefulness (Furth et al., 1994). Another approach has been developed which is based on the tetracycline-resistance operon tet from E. coli transposon Tn70. 

In plants, two kinds of metal-binding peptides or proteins are synthesized. Plant metallothioneins are inducible cysteine-rich entities very like those found in animals. Differential expression (induction) of metallothionein genes can be due to both variation of external heavy metal concentrations and the influence of various environmental factors. The principle role of plant metallothioneins seems to be in homeostasis rather than in metal detoxification. Plants are also known to have so-called phytochelatins, which are non-protein thiols specifically induced upon exposure to heavy metals. A close positive relationship between the concentrations of cadmium and phytochelatins in the plant shoot material has been observed and linked to the degree of growth inhibition (Keltjens and Van Beu-sichem, 1998). These observations make the use of phytochelatins promising for the assessment of heavy metal effect on plants. 

Beyersmann D (2002) Effects of carcinogenic metals on gene expression. Toxicol Lett 127 63-68. 

Gomes, S.J.C.M. and Brul, S., The effect of metal ions commonly present in food on gene expression of sporulating Bacillus subtilis cells in relation to spore wet heat resistance, Innov. Food Sci. Emerg. TechnoL, 5, 307, 2004. 

Miller AC, Brooks K, Smith J, Page N (2004) Effect of the militaiily-relevant heavy metals, depleted uranium and heavy metal tungsten-aUoy on gene expression in human liver carcinoma cells (HepG2). Mol Cell Biochem 255 247-256... 

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