Studies on the functional activity of the promoter for the human thyroid peroxidase gene.

We isolated the initial 1.3 kb of the 5'-flanking region of the human thyroid peroxidase (hTPO) gene, and sub-cloned this fragment into the luciferase reporter gene expression plasmid pA3-LUC. This plasmid contruct (p1.3HTPO-LUC) was stably transfected into FRTL5 rat thyroid cells and NIH-3T3 fibroblasts. Promoter activity was detected in 3 of 8 FRTL5 stable cell lines obtained. TSH, dBcAMP and phorbol ester did not alter TPO promoter activity. TPO promoter activity was also expressed in 4 of 5 NIH-3T3 stably-transfected cell lines, and this activity was also not altered by dBcAMP and phorbol ester. These data support the emerging concept that the TPO gene is not transcriptionally regulated by TSH and cAMP.