Transcriptional regulation of 3-methylcholanthrene-inducible P-450 gene responsible for metabolic activation of aromatic carcinogenes.
We have investigated the transcriptional regulation of 3-methylcholanthrene (3MC)-inducible P-450c gene which is involved in the metabolic activation of polycyclic aromatic carcinogens. Reverse genetic study using the fusion gene composed of the 5' upstream sequence of P-450c gene and the structure gene for bacterial chloramphenicol acetyltransferase (CAT) and a cultured cell line of Hepa-1 cells localized two kinds of cis-acting regulatory DNA elements. One is designated XRE or xenobiotic responsive element which is responsible for the inducibility of the gene and is distributed 5 times in the region from -3.0 to -0.5 kb. The other is BTE or basal transcription element whose deletion reduces a low level of the constitutive CAT expression to a background level, and which is localized immediately upstream of the TATA sequence. Both kinds of regulatory elements are necessary for a high level of inducible expression. Gel mobility shift assay strongly suggests that the binding protein to the XRE is an Ah receptor with a specific affinity for 3MC or 2,3,7,8,tetrachlorodibenzo-p-dioxin (TCDD). Without inducer treatment, cryptic form of the binding protein occurs only in the cytoplasm of the Hepa-1 cells. Upon treatment with the inducer, the cryptic form of the binding protein exhibits binding activity to XRE and, at the same time, translocates to the nuclei. The BTE-binding protein is an ubiquitous nuclear factor and its cDNA cloning reveals the DNA-binding feature with zinc finger motifs.
Fujii-Kuriyama
Y
Y
Department of Chemistry, Faculty of Science, Tohoku University, Sendai, Japan.
Sogawa
K
K
Imataka
H
H
Yasumoto
K
K
Kikuchi
Y
Y
Fujisawa-Sehara
A
A
D000818:Animals; D001483:Base Sequence; D015500:Chloramphenicol O-Acetyltransferase; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004742:Enhancer Elements, Genetic; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D008748:Methylcholanthrene / Q000494:pharmacology*; D008969:Molecular Sequence Data; D000072317:Polychlorinated Dibenzodioxins; D011401:Promoter Regions, Genetic; D051381:Rats; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
D000072317:Polychlorinated Dibenzodioxins; D015534:Trans-Activators; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D015500:Chloramphenicol O-Acetyltransferase