We have investigated regulatory DNA elements in the expression of the drug metabolizing P-450c gene of rats. Aftar combining the 5′ flanking and upstream untranslated regions of the isolated P-450c gene with structural gene for chloramphenicol acetyltransferase (CAT), the fusion genes were transfected into cultured cells (Kepa-1 and L cells) for the assay of transient expression of CAT activity. CAT activity was expressed inducibly in response to 3-methylcholanthrene only in Kepa-1 cells. At least three regions containing regulatory DNA elements were indentified; one, which is present in the sequence from -44b to -0.2kb immediately upstream of the TATA box, functions in the basal level of transcription, and the other two which were located in the sequence from -0.8kb to -1.0kb and from -1.0kb to -6.3kb, enhance in combination, transcription in response to inducers in a manner independent of their orientation.
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