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.
Morin
A
A
UAO 41115 CNRS, Laboratoire de Neuroendocrinologie Cellulaire, Collège de France, Paris.
Louette
J
J
Voz
M L
ML
Tixier-Vidal
A
A
Belayew
A
A
Martial
J A
JA
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