Differential expression of four linked sheep metallothionein genes.
Regulation of the closely linked endogenous sheep MT-Ia, MT-Ib, MT-Ic and MT-II genes by heavy metals and dexamethasone was studied in cultured sheep fibroblasts. Only MT-II mRNA was detectable before addition of any inducer. Addition of copper, zinc or cadmium salts to the culture medium increased the level of each mRNA; however, the magnitude of this response varied greatly between the four metallothionein genes. Following induction, levels of MT-Ia mRNA were the highest, followed by MT-II and MT-Ic mRNAs. The MT-Ib mRNA was only present at low levels. Zinc and cadmium were found to be the most effective inducers of each gene. The maximal response of the sMT-Ia, Ib and II genes to copper was only 30% of zinc and cadmium. The sMT-Ic gene responded very weakly to copper, less than 5% of the levels achieved with zinc. Only the MT-II mRNA increased in response to dexamethasone. In the liver of sheep on normal diets, the levels of MT-Ia, Ic and II mRNAs were found to be unexpectedly high and comparable to induced levels in fibroblasts.
Peterson
M G
MG
Murdoch Institute, Royal Children's Hospital, Parkville, Victoria, Australia.
Mercer
J F
JF
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D003470:Culture Media; D003907:Dexamethasone / Q000494:pharmacology; D004032:Diet; D005347:Fibroblasts; D005786:Gene Expression Regulation / Q000187:drug effects*; D005796:Genes; D008099:Liver / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D012756:Sheep / Q000235:genetics*; D015032:Zinc / Q000494:pharmacology
D003470:Culture Media; D012333:RNA, Messenger; D002104:Cadmium; D003300:Copper; D003907:Dexamethasone; D008668:Metallothionein; D015032:Zinc