Strucure and function of rat sodium/iodide symporter gene and its expression mechanism in the thyroid

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Iodide transport into the thyrocytes is the first step of the hormonogenesis and is important for diagnosis and treatment of various thyroid disease. To clarify these, we have cloned rat and human NIS gene and analyzed its structure and function of 5'-flanking region. As the results, we found that (1) the human NIS is a single copy gene mapped at No 19 chromosome (2) expression of NIS gene is stimulated by thyrotropin (TSH) (3) -291 to -134 bp (A in ATG codon is designated as +1) is important for its expression in the thyroid, and -420 to -370 bp is TSH-responsive element (4) thyroid transcription factor-1 (TTF-1) binds to -240 to -237 bp and stimulates NIS gene expression in the thyroid (5) unidentified but novel thyroid specific transcription factor binds to the -420 to -370 bp and might confers to the stimulation of NIS gene expression by TSH (6) NIS gene expression in thyroid cancer tissues is more higher than that in the normal surrounding tissues.These results might contribute to further understanding of iodide transport mechanism in the thyroid, especially in the thyroid cancer tissues, and also important for the diagnosis and treatment of various thyroid disease.