Siddique Aleem, Malo Madhu S, Ocuin Lee M, Hinnebusch Brian F, Abedrapo Mario A, Henderson J Welles, Zhang Wenying, Mozumder Moushumi, Yang Vincent W, Hodin Richard A
Department of Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts 02114, USA.
J Gastrointest Surg. 2003 Dec;7(8):1053-61; discussion 1061. doi: 10.1016/j.gassur.2003.09.006.
The gut-enriched Krüppel-like factor (KLF4) and the ligand-bound thyroid hormone receptor (TR) have each been shown to play a critical role in mammalian gut development and differentiation. We investigated an interrelationship between these two presumably independent pathways using the differentiation marker gene, intestinal alkaline phosphatase (IAP). Transient transfections were performed in Cos-7 cells using luciferase reporter plasmids containing a 2.5 kb segment of the proximal human IAP 5' regulatory region, as well as multiple deletions. Cells were cotransfected with TR and/or KLF4 expression vectors and treated+/-100 nmol/L thyroid hormone (T3). IAP reporter gene transactivation was increased independently by KLF4 (ninefold) and ligand-bound TR beta 1 (sevenfold). Cells cotransfected with KLF4 and TR beta 1 in the presence of T3 showed synergistic activation (70-fold). A similar pattern was seen with the other T3 receptor isoform, TR alpha 1. The synergistic effect was lost with deletions of the T3 and KLF4 response elements in the IAP promoter and was completely or partially abolished in the case of mutant KLF4 expression vectors. The thyroid hormone receptor complex and KLF4 synergistically activate the enterocyte differentiation marker gene IAP, suggesting a previously unrecognized interrelationship between these two transcription factor pathways.
肠道富集的Krüppel样因子（KLF4）和配体结合的甲状腺激素受体（TR）已各自被证明在哺乳动物肠道发育和分化中起关键作用。我们使用分化标记基因肠碱性磷酸酶（IAP）研究了这两条可能独立的途径之间的相互关系。使用含有近端人IAP 5'调控区2.5 kb片段以及多个缺失片段的荧光素酶报告质粒在Cos-7细胞中进行瞬时转染。细胞与TR和/或KLF4表达载体共转染，并接受±100 nmol/L甲状腺激素（T3）处理。IAP报告基因的反式激活分别由KLF4（增加9倍）和配体结合的TRβ1（增加7倍）独立增强。在T3存在下与KLF4和TRβ1共转染的细胞显示出协同激活（增加70倍）。另一种T3受体亚型TRα1也观察到类似模式。IAP启动子中T3和KLF4反应元件缺失时协同效应消失，并且在突变KLF4表达载体的情况下协同效应完全或部分消除。甲状腺激素受体复合物和KLF4协同激活肠上皮细胞分化标记基因IAP，提示这两条转录因子途径之间存在以前未被认识的相互关系。
