Lack of 12-O-tetradecanoylphorbol-13-acetate responsiveness of ornithine decarboxylase introns which have AP-1 consensus sequences.
The AP-1 consensus sequences (TGAGTCA) are the major 12-O-tetradecanoylphorbol113-acetate (TPA) responsive elements shared by several TPA inducible genes, such as c-sis, c-fos, c-myc, collagenase, stromelysin, hMTIIA and SV40. However, the role of AP-1 binding sites, which are present in the introns 3, 5, and 11 of ODC gene, in the regulation of TPA-induced ornithine decarboxylase (ODC) gene transcription are unknown. We determined the TPA responsiveness of the AP-1 sequences in the introns of ODC gene in CV-1 cells which induce ODC activity and mRNA in response to TPA treatment. ODC introns containing AP-1 sequences were inserted into the chloramphenicol acetyltransferase (CAT) reporter gene. Transient transfection of CV-1 cells with the intron-CAT constructs followed by TPA treatment did not induce CAT activity. However, when flanking regions of the AP-1 site in intron 3 were narrowed down to 74 bp, TPA induced CAT activity by 5- to 7-fold. The TPA-inducibility could be eliminated by mutation of the AP-1 site (TGAGTCA-->TGATGCCA or TGATGA) in 74 bp of intron 3. These results indicate that the AP-1 sequences in the intact ODC introns may not be responsive to TPA. The flanking sequences of the AP-1 site may be crucial to determine whether the AP-1 site is accessible to the TPA-induced transcriptional factor(s).
Tseng
C P
CP
Department of Human Oncology, University of Wisconsin Comprehensive Cancer Center, Madison 53792, USA.
Verma
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AK
D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D016384:Consensus Sequence; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D007438:Introns / Q000235:genetics; D009955:Ornithine Decarboxylase / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
D018808:Transcription Factor AP-1; D009955:Ornithine Decarboxylase; D013755:Tetradecanoylphorbol Acetate