Feliciello A, Allevato G, Musti A M, De Brasi D, Gallo A, Avvedimento V E, Gottesman M E
Dipartimento di Biologia e Patologia Molecolare e Cellulare, Centro di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università Federico II, Napoli, Italy.
Cell Growth Differ. 2000 Dec;11(12):649-54.
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).
甲状腺转录因子1（TTF1）是一种核同源结构域蛋白，它能结合并激活几种甲状腺特异性基因的启动子，包括甲状腺球蛋白基因（pTg）的启动子。这些基因也受到促甲状腺激素/环磷酸腺苷（cAMP）/蛋白激酶A（PKA）信号通路的正向调节。我们研究了PKA是否直接激活TTF1。我们发现，在几种细胞类型中，cAMP/PKA激活了pTg和携带TTF1结合位点重复序列的合成靶启动子。激活依赖于TTF1。磷酸肽图谱分析表明，TTF1在多个位点持续磷酸化，并且在体内cAMP刺激了其中一个位点丝氨酸337的磷酸化。然而，该残基或所有磷酸化位点的丙氨酸替代并没有降低PKA对pTg的激活。因此，PKA以间接方式刺激TTF1的转录活性，可能是通过招募或从靶启动子上移除另一种调节因子。
