Thyroid transcription factor 1 phosphorylation is not required for protein kinase A-dependent transcription of the thyroglobulin promoter.
Thyroid transcription factor 1 (TTF1) is a nuclear homeodomain protein that binds to and activates the promoters of several thyroid-specific genes, including that of the thyroglobulin gene (pTg). These genes are also positively regulated by thyroid-stimulating hormone/cyclic AMP (cAMP)/protein kinase A (PKA) signaling. We asked whether PKA directly activates TTF1. We show that cAMP/PKA activates pTg and a synthetic target promoter carrying TTF1 binding site repeats in several cell types. Activation depends on TTF1. Phosphopeptide mapping indicates that TTF1 is constitutively phosphorylated at multiple sites, and that cAMP stimulated phosphorylation of one site, serine 337, in vivo. However, alanine substitution at this residue or at all sites of phosphorylation did not reduce PKA activation of pTg. Thus, PKA stimulates TTF1 transcriptional activity in an indirect manner, perhaps by recruiting to or removing from the target promoter another regulatory factor(s).
Feliciello
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A
Dipartimento di Biologia e Patologia Molecolare e Cellulare, Centro di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università Federico II, Napoli, Italy.
Allevato
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G
Musti
A M
AM
De Brasi
D
D
Gallo
A
A
Avvedimento
V E
VE
Gottesman
M E
ME
D000409:Alanine / Q000737:chemistry; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D016895:Culture Media, Serum-Free; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D016716:PC12 Cells; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D051381:Rats; D013954:Thyroglobulin / Q000235:genetics*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D016895:Culture Media, Serum-Free; C000614412:NKX2-1 protein, human; C000614416:Nkx2-1 protein, rat; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D013954:Thyroglobulin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000409:Alanine