A thyroid-specific far-upstream enhancer in the human sodium/iodide symporter gene requires Pax-8 binding and cyclic adenosine 3',5'-monophosphate response element-like sequence binding proteins for full activity and is differentially regulated in normal and thyroid cancer cells.
The sodium/iodide symporter (NIS) gene is highly expressed in the thyroid gland and is important for the diagnosis and radioiodide therapy of differentiated thyroid cancers. We investigated a human NIS (hNIS) gene 5'-far-upstream enhancer (hNUE) (-9847 to -8968). The hNUE is TSH responsive in both FRTL-5 cells and primary normal thyroid cells, but not in human papillary thyroid cancer cells (BHP cells). The hNUE enhanced expression of the basal hNIS promoter 15-fold and required both a Pax-8 binding site and a cAMP response element (CRE)-like sequence for full activity. The hNUE activated transcription in a thyroid-selective and cAMP-dependent manner, mediated by both protein kinase A (PKA)-dependent and PKA-independent pathways. Pax-8 and two CRE-like sequence binding proteins bind to the hNUE. Supershift binding assay indicated that one of the CRE-like sequence binding protein(s) was CRE-binding protein-1, activation transcription factor-1, and/or CRE modulator, and the other was an unknown factor(s) that is absent in BHP 2-7 cells. A far-upstream enhancer is important for hNIS regulation in the thyroid. Deficient CRE-like sequence binding protein(s) that bind to the hNUE in normal thyroid cells may be responsible for reduced NIS gene expression in some thyroid carcinomas.
D051698:Activating Transcription Factor 2; D000818:Animals; D001665:Binding Sites; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic; D051381:Rats; D012016:Reference Values; D020218:Response Elements / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D027981:Symporters / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D013961:Thyroid Gland / Q000166:cytology / Q000502:physiology*; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000099209:Sodium-Iodide Symporters
D051698:Activating Transcription Factor 2; D000242:Cyclic AMP; D017362:Cyclic AMP Response Element-Binding Protein; D017868:Cyclic AMP-Dependent Protein Kinases; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; D027981:Symporters; D000074482:Thyroid Nuclear Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; D000099209:Sodium-Iodide Symporters; C083325:PAX8 protein, human; C499497:Pax8 protein, rat