TTF-2 does not appear to be a key mediator of the effect of cyclic AMP on thyroglobulin gene transcription in primary cultured dog thyrocytes.
TTF-2 is a thyroid-specific winged-helix transcription factor which has been proposed to play a key role in the hormonal control of thyroglobulin and thyroperoxidase genes transcription in FRTL-5 cells. We have analyzed TTF-2 DNA-binding activity in primary cultures of dog thyrocytes maintained in control condition or in the presence of the cAMP agonist forskolin. Binding of 35S-labelled nuclear proteins to the TTF-2 recognition sequence identified the presence of two molecular species of 41.5 and 42.5 kDa. TTF-2 DNA-binding activity was clearly detectable in nuclear extracts from unstimulated cells and appeared increased in forskolin-treated cells. Thus, the presence of TTF-2 DNA-binding activity does not correlate with the cAMP-dependent activity of thyroglobulin and thyroperoxidase genes in this cell system. In addition, the mutation of the TTF-2 binding site in the thyroglobulin promoter resulted in a very reduced but still clearly cAMP-dependent promoter activity when assayed by transient expression in the same cells. These results do not support a dominant role for TTF-2 in the cAMP-dependent control of thyroglobulin gene transcription in primary cultured thyrocytes.
Pouillon
V
V
I.R.I.B.H.N., Université Libre de Bruxelles, Faculté de Médecine, Belgium.
Pichon
B
B
Donda
A
A
Christophe
D
D
D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D051858:Forkhead Transcription Factors; D005786:Gene Expression Regulation / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D009195:Peroxidase / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D013462:Sulfur Radioisotopes; D013954:Thyroglobulin / Q000235:genetics*; D013961:Thyroid Gland / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection / Q000235:genetics
D004268:DNA-Binding Proteins; C106894:FOXE1 protein, human; D051858:Forkhead Transcription Factors; D009687:Nuclear Proteins; D012097:Repressor Proteins; D013462:Sulfur Radioisotopes; D005576:Colforsin; D013954:Thyroglobulin; D000242:Cyclic AMP; D009195:Peroxidase