Metal-dependent binding of a factor in vivo to the metal-responsive elements of the metallothionein 1 gene promoter.
Mol Cell Biol
; 7(10): 3574-81, 1987 Oct.
Article
em En
| MEDLINE
| ID: mdl-3683394
ABSTRACT
Using the technique of genomic footprinting, we demonstrate cadmium-inducible protection from dimethyl sulfate (DMS) modification of guanine residues in vivo in five metal-responsive elements (MREs) in the promoter of the rat metallothionein 1 (MT-1) gene. We also identify a site of extreme DMS hyperreactivity which, like the MRE protection, occurs only after metal ion induction. With this hyperreactive site as an indicator, we can measure the kinetics of induction and deinduction. Changes in the intracellular metal ion concentrations are reflected in alterations in the reactivity with DMS of guanine residues in the MT-1 gene promoter. Lastly, for both control and metal-induced cells, we observe DMS protection and enhancement of a binding site (located 5' of the distal MRE) which is a consensus sequence for the Sp1 transcription factor. Transfection experiments with deletion mutations of a fusion gene construct indicate both that a sequence region which includes this GC box regulates the basal level of expression of the MT-1 gene and that increasing the number of MREs in the promoter increases the induced level of transcription. Our genomic footprinting and transfection data together suggest that (i) a transcription factor, possibly Sp1, plays an important role in regulating the basal level of expression of the MT-1 gene and (ii) metal induction involves the metal-dependent binding to a sequence-specific binding factor which responds to changes in intracellular metal ion levels.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fatores de Transcrição
/
Cádmio
/
Regiões Promotoras Genéticas
/
Proteínas de Ligação a DNA
/
Metalotioneína
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
Mol Cell Biol
Ano de publicação:
1987
Tipo de documento:
Article