title: Dioxin-inducible enhancer region upstream from the mouse P(1)450 gene and interaction with a heterologous SV40 promoter.
abstract: In mouse hepatoma Hepa-1 cells, polycyclic aromatic compounds such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) activate transcription of the mouse P(1)450 gene via trans-acting regulatory factors that include the TCDD X receptor complex. The positive control element in the P(1)450 5'-flanking region was examined in control and TCDD-treated Hepa-1 stable transformants that had been transfected with either of two expression vectors containing the chloramphenicol acetyltransferase (CAT) gene: pA10-cat, which has the simian virus 40 (SV40) early core promoter (without enhancers) immediately upstream from the CAT gene; and pSV0-cat, which has no promoter or enhancer. When the 1-kb DNA fragment from -1,647 to -611 upstream from the P(1)450 gene is inserted in either orientation--immediately upstream or almost 2 kb further upstream--from the SV40 promoter in pA10-cat, there is enhancement of CAT activity that can be further induced three- to fourfold by TCDD. When the same experiment is carried out with the -1,247 to -823 fragment or the -1,051 to -823 fragment, but not the -1,247 to -1,052 fragment, TCDD responsiveness is lost, or at least masked, because of a large increase in constitutive CAT activity. pSV0-cat mutants containing internal deletions in the upstream flanking sequences of P(1)450 were constructed. A region of 300 bases (-1,218 to -918) is shown to be required for TCDD responsiveness, and one TCDD-inducible element can be dissociated from an enhancer of constitutive gene expression, whereas one or more other TCDD-inducible elements cannot.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000123:Acetyltransferases / Q000235:genetics; D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase; D002874:Chromosome Mapping; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004274:DNA, Recombinant; D004147:Dioxins / Q000494:pharmacology*; D004742:Enhancer Elements, Genetic; D004790:Enzyme Induction / Q000187:drug effects; D005809:Genes, Regulator; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D013539:Simian virus 40
chemical_list: D004274:DNA, Recombinant; D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D003577:Cytochrome P-450 Enzyme System; D000123:Acetyltransferases; D015500:Chloramphenicol O-Acetyltransferase