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Zinc Rapidly Induces a Metal Response Element-Binding Factor
Marta Czupryn, Willis E. Brown and Bert L. Vallee
Proceedings of the National Academy of Sciences of the United States of America
Vol. 89, No. 21 (Nov. 1, 1992), pp. 10395-10399
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2360616
Page Count: 5
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Metal activation of metallothionein gene transcription is mediated by specific promoter sequences, termed metal regulatory elements (MREs). Nuclear extracts prepared from various human cell lines were assayed for their capacity to bind to a synthetic human MREa (hMREa) oligomer. Electrophoretic mobility-shift assays with extracts from control cells detected a single hMREa-containing complex. Addition to the growth medium of zinc, cadmium, or copper-metals known to induce MT biosynthesis in vivo-resulted in the rapid but reversible appearance of a second distinct hMREa-protein complex in all cell lines studied. This result was not seen when the metals were added directly to the extracts from control cells. DNA-binding protein blotting, UV crosslinking, and electroelution experiments were used to characterize the two hMREa-binding factors, termed BF1 and BF2. MRE-BF1 has an apparent molecular mass of ≈86 kDa and binds to the hMREa in control cells, whereas MRE-BF2 consists of two molecules of ≈28 kDa and binds to the hMREa in metal-treated cells. EDTA and o-phenanthroline inhibited binding of both factors to hMREa in a dose-dependent manner, indicating that a metal atom or atoms are essential for interaction of the factors with DNA.
Proceedings of the National Academy of Sciences of the United States of America © 1992 National Academy of Sciences