Characterization of a thyroid-specific and cyclic adenosine monophosphate-responsive enhancer far upstream from the human sodium iodide symporter gene.
We describe the cloning and characterization of a human sodium iodide (NIS) upstream enhancer (NUE). This putative enhancer was cloned based on its sequence homology (69% identity) to the rat NUE. A 296 base pair (bp) genomic DNA fragment, which is located 9000 bp upstream from the human hNIS gene, was amplified by polymerase chain reaction (PCR) and inserted into a luciferase reporter gene in front of both the homologous NIS promoter and the heterologous SV40 promoter. No enhancer activity could be found after transfection into HeLa cells, but in FRTL-5 cells representing the thyroid model, a threefold stimulation of the NIS promoter was found. This enhancer activity was present in both directions and was stimulated threefold by thyrotropin (TSH) and 14-fold by the cyclic adenosine monophosphate (cAMP) agonist forskolin. A small element (TGACGCA) in this enhancer was found to be of central importance, because its site-directed mutagenesis abolished the enhancer activity. This element bound specifically to proteins in nuclear extracts from FRTL-5 cells and to a lesser extent also from HeLa cells. In summary, we describe a thyroid-specific and cAMP-responsive enhancer far upstream from the human NIS gene, which is located in the intronic region of another gene coding for a ribosomal protein.
Schmitt
Thomas L
TL
Department of Internal Medicine I, University Clinic of Ulm, Germany.
Espinoza
Celia R
CR
Loos
Ulrich
U
D000818:Animals; D001483:Base Sequence / Q000235:genetics; D002460:Cell Line; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000502:physiology*; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000502:physiology; D051381:Rats; D027981:Symporters / Q000235:genetics*; D013961:Thyroid Gland / Q000502:physiology*; D014162:Transfection; D000099209:Sodium-Iodide Symporters
D000242:Cyclic AMP; D004247:DNA; D027981:Symporters; D000099209:Sodium-Iodide Symporters