Triiodothyronine inhibits transcription from the human growth hormone promoter.
Three DNA constructs, the natural human growth hormone gene (hGH-hGH) its 500 bp promoter linked to the chloramphenicol acetyl transferase reporter gene (hGH-CAT), and its structural part linked to the herpes virus thymidine kinase promoter (TK-hGH) were introduced into rat pituitary GC cells by DEAE-dextran transfection. Transient expression was followed as a function of triiodothyronine (T3) concentration. The hGH-CAT expression was specifically inhibited by T3 following a typical dose-response curve while hGH-GH gene expression was not significantly modified. The transient expression of TK-hGH increased as a function of T3 concentration. These results indicate that T3 exerts two opposite effects on hGH gene expression. First, it down-regulates expression by acting on the promoter; second, it up-regulates expression by acting on the structural part of the gene. These action could be due to regulation of transcription and mRNA stabilization, respectively.
UAO 41115 CNRS, Laboratoire de Neuroendocrinologie Cellulaire, Collège de France, Paris.
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Morin
J
J
Louette
M L
ML
Voz
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Tixier-Vidal
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Belayew
J A
JA
Martial
D000818:Animals; D005786:Gene Expression Regulation / Q000187:drug effects*; D005796:Genes / Q000187:drug effects; D013006:Growth Hormone / Q000235:genetics*; D006561:Herpes Simplex / Q000235:genetics; D010911:Pituitary Neoplasms / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013937:Thymidine Kinase / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*; D014284:Triiodothyronine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D011993:Recombinant Fusion Proteins; D014284:Triiodothyronine; D013006:Growth Hormone; D013937:Thymidine Kinase