Down-regulation of calcitonin gene transcription by vitamin D requires two widely separated enhancer sequences
| Autor: | C W Cooper, Robert F. Gagel, Ronald V. Abruzzese, Sara Peleg |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Calcitonin
24 25-Dihydroxyvitamin D 3 Transcription Genetic Recombinant Fusion Proteins Molecular Sequence Data E-box Enhancer RNAs Biology Endocrinology Calcitriol Transcription (biology) Cyclic AMP Tumor Cells Cultured Humans Thyroid Neoplasms Enhancer Molecular Biology Gene Reporter gene Base Sequence General transcription factor General Medicine TCF4 Molecular biology Enhancer Elements Genetic Gene Expression Regulation Carcinoma Medullary Depression Chemical Receptors Calcitriol |
| Zdroj: | Molecular Endocrinology. 7:999-1008 |
| ISSN: | 1944-9917 0888-8809 |
| DOI: | 10.1210/mend.7.8.8232320 |
| Popis: | Transcription of the calcitonin (CT) gene is down-regulated by vitamin D in normal and transformed thyroid C cells. DNA transfer techniques have been previously used to map and characterize a cAMP-induced enhancer at nucleotides -255 to -129 and an enhancer of basal transcription at -1060 to -905 in the CT 5' flanking DNA. The same methods were used to identify a negative response element for vitamin D. Deletion mutants of a genomic fragment of CT extending from nucleotides -1460 to +90 were attached to a promoterless GH gene and transfected individually into the medullary thyroid carcinoma cell line TT. CT nucleotides -1460 to -129 induced significant basal transcription of the GH reporter gene in TT cells. Basal transcription was elevated 3-fold to 4-fold by treatment with cAMP analog. The biologically active metabolite of vitamin D3, 1,25-dihydroxyvitamin D3, had a minor (20%) inhibitory effect on basal transcription but inhibited more than 60% of the cAMP-induced transcription. We further investigated the cAMP-induced response and found that transcriptional activity of the downstream cAMP-induced enhancer was greatly synergized in the presence of the upstream enhancer of basal transcription. The latter enhancer contained three functional CANNTG sequences designated E1 (nucleotides -1060 to -1030), E2 (nucleotides -940 to -920), and E3 (nucleotides -920 to -900). E2 and E3 were essential for maximal cAMP-induced transcription. Detailed mapping of the vitamin D response showed that a minimum requirement for inhibition of the cAMP-induced enhancer by vitamin D was a sequence overlapping E3 (nucleotides -920 to -829). We conclude that a negative response element to vitamin D is located between nucleotides -920 and -829 in the CT 5' flanking DNA. It is possible that vitamin D inhibits transcription by interfering with the synergistic interaction between the cAMP-induced enhancer and the enhancer of basal transcription. |
| Databáze: | OpenAIRE |
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