Summary:
The regulation of the human Na+/I- symporter (NIS) gene is of considerable interest for both the diagnosis and therapy
of thyroid pathologies. We investigated the influence of the thyroid-specific transcription
factors TTF-1 and Pax8 on the NIS promoter and its 5′-flanking sequence. Reporter
genes containing the corresponding genomic fragments coupled to a luciferase reporter
gene were cotransfected with expression vectors carrying the the cDNA's for TTF-1
and Pax8. Transient transfection assays were performed in HeLa and COS-7 cells, which
do not express endogenously these transcription factors. The experiments showed, that
TTF-1 had no influence on the NIS promoter. Pax8, on the other hand, had a moderate
stimulating effect (threefold) on the proximal NIS promoter. ABCD assays indicated
an interaction of in vitro-translated Pax8 with the NIS promoter. However, DNase I footprinting experiments
with bacterially expressed Pax8 were negative, suggesting an indirect mode of action
with the participation of other proteins. A putative NIS upstream enhancer (NUE) 9000
bp upstream of the NIS gene, which was cloned based on its sequence homology to the
rat NUE, was not transactivated by either Pax8 or TTF-1. The present data demonstrate,
that the combination of Pax8 and TTF-1 is less important for NIS gene transcription
than for other thyroid-specific genes. This is presumably related to the fact, that
NIS is expressed also in other tissues such as mammary and salivary gland.
Key words:
NIS - iodide transport - promoter - transcription factors - thyroglobulin
References
- 1
Behr M, Schmitt T L, Espinoza C R, Loos U.
Cloning of a functional promoter of the human sodium/iodide-symporter gene.
Biochem J.
331
359-363
1998;
- 2
Christophe D, Cabrer B, Bacolla A, Targovnik H, Pohl V, Vassart G.
An unusually long poly(purine)-poly(pyrimidine) sequence is located upstream from
the human thyroglobulin gene.
Nucl. Acids Res.
13
5127-5144
1985;
- 3
Damante R, Di Lauro R.
Thyroid-specific gene expression.
Biochim. Biophys. Acta.
1218
255-266
1994;
- 4
Eberhard D, Busslinger M.
The partial homeodoamin of the transcription factor Pax-5 (BSAP) is an interaction
motif for the retinoblastoma and TATA-binding proteins.
Cancer Res.
59
((Suppl))
1716s-1725s
1999;
- 5
Esposito C, Miccadei S, Saiardi A, Civitareale D.
Pax8 activates the enhancer of the human thyroperoxidase gene.
Biochem. J.
331
37-40
1998;
- 6
Hamdan H, Liu H, Li C, Jones C, Lee M, deLemos R, Minoo P.
Structure of the human Nkx2.1 gene.
Biochim. Biophys. Acta.
1396
336-348
1998;
- 7
Jhiang S, Cho J, Ryu K, DeYoung B, Smanik P, McGaughy V, Fischer A, Mazzaferri E.
An immunohistochemical study of Na+/I-symporter in human thyroid tissues and salivary gland tissues.
Endocrinol.
139
4416-4419
1998;
- 8
Macchia P, Lapi P, Krude H, Pirro M, Missero C, Chiovato L, Souabni A, Baserga M,
Tassi V, Pinchera A, Fenzi G, Grüters A, Busslinger M, Di Lauro R.
Pax8 mutations associated with congenital hypothyroidism caused by thyroid dysgenesis.
Nature Genetics.
19
83-86
1998;
- 9
Mansouri A, Chowdhury K, Gruss P.
Follicular cells of the thyroid gland require Pax8 gene function.
Nature Genetics.
19
87-90
1998;
- 10
Musti A M, Ursini V M, Avvedimento E V, Zimarino V, Di Lauro R.
A cell type specific factor recognizes the rat thyroglobulin promoter.
Nucleic Acids Res.
15
8149-8166
1987;
- 11
Ohno M, Zannini M, Levy O, Carrasco N, Di Lauro R.
The paired domain transcription factor Pax8 binds to the upstream enhancer of the
rat sodium/iodide symporter gene and participates in both thyroid-specific and cyclic-AMP
dependent transcription.
Mol. Cell Biol.
19
2051-2060
1999;
- 12
Poleev A, Fickenscher H, Mundlos S, Winterpacht A, Zabel B, Fidler A, Gruss P, Plachov D.
Pax8, a human paired-box gene: isolation and expression in developing thyroid, kidney
and Wilms' tumors.
Development.
116
611-623
1992;
- 13
Ryu K, Tong Q, Jhiang S M.
Promoter characterization of the human Na/I symporter.
J. Clin. Endocrinol. Metab.
83
3247-3251
1998;
- 14
Schmitt T L, Espinoza C R, Loos U.
Cloning and characterization of repressory and stimulatory DNA sequences upstream
the Na/I- symporter gene promoter.
Horm Metab. Res.
32
1-5
2000;
- 15
Smanik P A, Liu Q, Furminger T L, Ryu K, Xing S, Mazzaferri E L, Jhiang S M.
Cloning of the human sodium iodide symporter.
Biochem. Biophys. Res. Commun.
226
339-345
1996;
- 16
Spitzweg C, Joba W, Eisenmenger W, Heufelder A E.
Analysis of human sodium iodide symporter gene expression in extrathyroidal tissues
and cloning of its complementary deoxyribonucleic acids from salivary gland, mammary
gland, and gastric mucosa.
J. Clin. Endocrinol. Metab.
83
1746-1751
1998;
- 17
Tazebay U, Wapnir I, Levy O, Orsolya D, Zuckier L, Zhao Q H, Deng H F, Amenta P, Fineberg S,
Pestell R, Carrasco N.
The mammary gland iodide transporter is expressed during lactation and in breast cancer.
Nat. Med.
6
871-878
2000;
- 18
Venkataraman G, Yatin M, Ain K B.
Cloning of the human sodium-iodide symporter promoter and characterization in a differentiated
human thyroid cell line, KAT-50.
Thyroid.
8
63-69
1998;
- 19
Zannini M, Francis-Lang H, Plachov D, DiLauro R.
Pax-8, a paired domain-containing protein, binds to a sequence overlapping the recognition
site of a homeodomain and activates transcription from two thyroid-specific promoters.
Mol. Cell Biol.
12
4230-4241
1992;
1 * Both authors contributed equally to this work
Dr. Thomas Schmitt
Abteilung Innere Medizin I
Universitätsklinikum Ulm
Robert-Koch-Straße 8
D-89081 Ulm
Telefon: + 49-731-502-4741
Fax: + 49-731-502-4745
eMail: thomas.schmitt@medizin.uni-ulm.de