Internal genomic sequence of human CYP1A1 gene is involved in superinduction of dioxin-induced CYP1A1 transcription by cycloheximide.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces CYP1A1 mRNA expression, and co-treatment with the protein synthesis inhibitor, cycloheximide (CHX) magnifies its expression severalfold further. Although this phenomenon has been reported as superinduction, its molecular mechanism is still obscure. In the present study, we analyzed the influence of the CYP1A1 internal genomic sequence on CHX-mediated superinduction. Partial sequences of the human CYP1A1 were inserted at the 5' end of the internal ribosomal entry site (IRES) connected to luciferase cDNA, and generated constructs were transiently transfected into CHO or HepG2 cells. Intron-1 deletion constructs showed higher inductivity than intron-1 intact constructs by TCDD. Quantitative RT-PCR analyses revealed that the superinduced levels by CHX of the intron-1 intact constructs were greater than those of the intron-1 deletion constructs. The present results indicate that internal genomic sequences of the human CYP1A1 gene, especially the internal sequence of intron-1, are involved in superinduction of the CYP1A1 gene by CHX.
Sakata
Yoshinori
Y
Division of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan.
Yoshioka
Wataru
W
Tohyama
Chiharu
C
Ohsako
Seiichiroh
S
D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003513:Cycloheximide / Q000494:pharmacology*; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics*; D004147:Dioxins / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D015894:Genome, Human; D006801:Humans; D007438:Introns / Q000235:genetics; D049410:Luciferases, Renilla / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects* / Q000235:genetics
D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D011500:Protein Synthesis Inhibitors; D003513:Cycloheximide; D049410:Luciferases, Renilla; D019363:Cytochrome P-450 CYP1A1