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DOI: 10.1055/s-2001-11021
© Johann Ambrosius Barth
Characterization of the upstream enhancer of the rat sodium/iodide symporter gene
Publication History
Publication Date:
31 December 2001 (online)
![](https://www.thieme-connect.de/media/eced/200101/lookinside/thumbnails/10.1055-s-2001-11021-1.jpg)
Summary:
We previously demonstrated the presence of an enhancer that is located between nucleotides - 2264 and - 2495 in the 5′ flanking region of the rat sodium/iodide symporter (NIS) gene ([Ohno et al., 1999]). When attached to NIS or heterologous promoters, this 232 bp fragment, which we call NUE, is able to stimulate transcription in a thyroid-specific and cAMP-dependent manner. A paired-domain transcription factor Pax8 binds to this enhancer and can stimulate the transcription in non-thyroid cells that do not normally support the NUE activities. Cotransfection of PKA, a downstream effector of cAMP, further potentiates the Pax8-mediated transactivation. However, this transcriptional machinery containing pax8 seems to require contributions from the neighboring cis-acting element that is similar to CRE/AP-1 consensus sequences. Modification of this putative CRE/AP-1 site not only represses the NUE transcriptional activities by 90% in FRTL-5 cells, but also nullifies the synergistic effect of PKA on pax8-mediated transactivation in HeLa cells. In this report, we have further characterized the putative CRE/AP-1 site within the NIS upstream enhancer using gel mobility shift assay. An oligonucleotide probe with NIS CRE/AP-1 sequence produced complex binding patterns in both FRTL-5 and HeLa cell, reflecting the presence of diverse classes of binding factors. When compared with CRE or AP-1 elements in other genes, the mobility shift pattern of NIS CRE/AP-1 was similar to those of collagenase TRE, c-Jun TRE, and somatostatin CRE, but the relative intensities of the binding complexes were quite different. This observation raises a possibility that the NIS CRE/AP-site is regulated by a novel mechanism.
Key words:
NIS - AP-1 - cAMP - Rap1 - Pax8
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J. T. ChunPh.D.
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