Zinc-specific activation of a HeLa cell nuclear protein which interacts with a metal responsive element of the human metallothionein-IIA gene.
Transcription of metallothionein genes is activated by heavy metals such as zinc and cadmium, and a DNA element called metal responsive element (MRE) is essential for this process. By mobility-shift assay, we identified a HeLa-cell nuclear protein which specifically binds to MREa of human metallothionein-IIA gene. This protein, named ZRF (zinc-regulatory factor), is present in the cells untreated with heavy metals. Zinc is essential for, and increases in a dose-dependent manner, the binding of ZRF to MREa. Other heavy metals which can also induce metallothioneins, including cadmium, copper and mercury, do not activate ZRF. A MREa-containing oligonucleotide that can bind ZRF confers heavy metal-inducibility to a heterologous promoter, suggesting that ZRF is a zinc-dependent transcriptional activator. In addition to the MRE core sequence, the surrounding sequences are also important for both ZRF binding in vitro, and zinc-dependent transcriptional activation in vivo. MREa by itself responds not only to zinc but also to other metallothionein-inducing heavy metals, indicating that the ZRF protein, not the MREa sequence, is responsible for the zinc specificity.
Koizumi
S
S
Department of Experimental Toxicology, National Institute of Industrial Health, Kawasaki, Japan.
Yamada
H
H
Suzuki
K
K
Otsuka
F
F
D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002104:Cadmium / Q000494:pharmacology; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells / Q000737:chemistry*; D006801:Humans; D008668:Metallothionein / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid; D013937:Thymidine Kinase / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection; D015032:Zinc / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D002104:Cadmium; D004247:DNA; D008668:Metallothionein; D015500:Chloramphenicol O-Acetyltransferase; D013937:Thymidine Kinase; D015032:Zinc