Yi Ming, Tong Guo-Xia, Murry Barbara, Mendelson Carole R
Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9038, USA.
J Biol Chem. 2002 Jan 25;277(4):2997-3005. doi: 10.1074/jbc.M109793200. Epub 2001 Nov 16.
Surfactant protein-A (SP-A) gene expression is developmentally regulated in fetal lung type II cells and is enhanced by cAMP. cAMP stimulation of SP-A gene expression is mediated by protein kinase A (PKA) phosphorylation of thyroid transcription factor 1 (TTF-1), expressed selectively in developing lung epithelium. In this study, we analyzed roles of CREB-binding protein (CBP) and steroid receptor coactivator-1 (SRC-1) in TTF-1 regulation of SP-A expression. Upon differentiation of human fetal lung in culture, nuclear localization of CBP, SRC-1, and TTF-1 increased in ductular epithelium in association with type II cell differentiation and induction of SP-A expression. In transient transfections, CBP and SRC-1 acted synergistically with TTF-1 to increase SP-A promoter activity. Overexpression of PKA catalytic subunit enhanced hSP-A promoter activation by SRC-1 plus TTF-1. Adenoviral E1A overexpression reduced TTF-1 +/- SRC-1 induction of SP-A promoter activity, suggesting a role of endogenous CBP/p300. TTF-1 interacted with SRC-1 and CBP in vitro. SRC-1 immunodepletion from type II cell nuclear extracts reduced binding to the TTF-1 binding element upstream of SP-A gene. In cultured type II cells, cAMP increased TTF-1 acetylation. This suggests that cAMP-mediated TTF-1 phosphorylation facilitates interaction with CBP and SRC-1, resulting in its hyperacetylation, further enhancing TTF-1 DNA-binding and transcriptional activity.
表面活性蛋白A（SP-A）基因表达在胎儿肺II型细胞中受到发育调控，并被cAMP增强。cAMP对SP-A基因表达的刺激是由甲状腺转录因子1（TTF-1）的蛋白激酶A（PKA）磷酸化介导的，TTF-1在发育中的肺上皮细胞中选择性表达。在本研究中，我们分析了CREB结合蛋白（CBP）和类固醇受体辅激活因子-1（SRC-1）在TTF-1对SP-A表达调控中的作用。在培养的人胎儿肺分化过程中，CBP、SRC-1和TTF-1的核定位在导管上皮细胞中增加，与II型细胞分化和SP-A表达的诱导相关。在瞬时转染中，CBP和SRC-1与TTF-1协同作用以增加SP-A启动子活性。PKA催化亚基的过表达增强了SRC-1加TTF-1对hSP-A启动子的激活。腺病毒E1A的过表达降低了TTF-1 +/- SRC-1对SP-A启动子活性的诱导，提示内源性CBP/p300的作用。TTF-1在体外与SRC-1和CBP相互作用。从II型细胞核提取物中免疫去除SRC-1减少了与SP-A基因上游TTF-1结合元件的结合。在培养的II型细胞中，cAMP增加了TTF-1的乙酰化。这表明cAMP介导的TTF-1磷酸化促进了与CBP和SRC-1的相互作用，导致其超乙酰化，进一步增强TTF-1的DNA结合和转录活性。
