Morrisey E E, Musco S, Chen M Y, Lu M M, Leiden J M, Parmacek M S
Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
J Biol Chem. 2000 Jun 30;275(26):19949-54. doi: 10.1074/jbc.M001331200.
Gene targeting studies have demonstrated that the zinc finger transcription factor GATA-6 lies upstream in a transcriptional cascade that controls differentiation of the visceral endoderm. To understand the function of GATA-6 in the visceral endoderm and to identify genes regulated by GATA-6 in this tissue, subtractive hybridization was performed using template cDNAs derived from differentiated wild-type embryonic stem (ES) cells and GATA-6(-/-) ES cells, respectively. These analyses revealed that the gene encoding Dab2, a mitogen-responsive phosphoprotein, is differentially expressed in wild-type and GATA-6-deficient ES cells. Consistent with these findings, Dab2 is expressed in the visceral endoderm of wild-type embryos but not in the visceral endoderm of GATA-6-deficient embryos. Cotransfection experiments demonstrate that the human Dab2 promoter can be transactivated by forced expression of GATA-6 in NIH-3T3 cells. In contrast, forced expression of GATA-4 does not transactivate the human Dab2 promoter and Dab2 is expressed in the visceral endoderm of GATA-4 null embryos. Surprisingly, the specificity of GATA-6-induced transactivation of the Dab2 promoter is not mediated through its zinc finger DNA-binding domain. Taken together, these data demonstrate that the mitogen-responsive phosphoprotein Dab2 is a downstream target of GATA-6 in the visceral endoderm. Moreover, these data demonstrate that molecular mechanisms have evolved that direct, and distinguish, the functional specificity of GATA family members when they are developmentally coexpressed.
基因靶向研究表明，锌指转录因子GATA-6在内脏内胚层分化调控的转录级联反应中处于上游位置。为了解GATA-6在内脏内胚层中的功能，并鉴定该组织中受GATA-6调控的基因，分别使用来自分化的野生型胚胎干细胞（ES细胞）和GATA-6（-/-）ES细胞的模板cDNA进行了消减杂交。这些分析表明，编码有丝分裂原反应性磷蛋白Dab2的基因在野生型和GATA-6缺陷型ES细胞中差异表达。与这些发现一致，Dab2在野生型胚胎的内脏内胚层中表达，但在GATA-6缺陷型胚胎的内脏内胚层中不表达。共转染实验表明，在NIH-3T3细胞中，GATA-6的强制表达可激活人Dab2启动子。相反，GATA-4的强制表达不能激活人Dab2启动子，并且Dab2在GATA-4缺失胚胎的内脏内胚层中表达。令人惊讶的是，GATA-6诱导的Dab2启动子激活的特异性不是通过其锌指DNA结合结构域介导的。综上所述，这些数据表明有丝分裂原反应性磷蛋白Dab2是内脏内胚层中GATA-6的下游靶点。此外，这些数据表明，当GATA家族成员在发育过程中共表达时，已经进化出了指导和区分其功能特异性的分子机制。
