TRANSCRIPTION FACTOR INTERACTIONS AT THE GH PROMOTER

生长激素（GH）是一种强大的线性生长和代谢稳态调节剂，作用于几乎所有器官系统。外源性生长激素治疗是昂贵的，但有效地抵消了深刻的代谢影响与特发性生长激素缺乏症，似乎，正常的年龄相关的下降生长激素基因转录。 GH合成仅限于垂体前叶的促生长细胞，其中GH基因的转录通过全身和下丘脑激素以不同的生理、年龄相关和昼夜节律模式受到严格调节，其中许多激素通过蛋白激酶系统起作用。我们的长期目标是确定激素调节的生长激素特异性GH基因表达的分子机制，作为设计靶向GH转录的经济有效疗法的第一步。 转录因子C/EBPalpha与垂体特异性转录因子Pit-1和共激活因子CBP协同控制蛋白激酶A和C调节的GH基因转录。 协同激活可能源于C/EBPalpha、Pit-1和CBP在特定基础因子和/或结构靶点的相互或互补的激酶调节作用。C/EBPalpha、Pit-1和CBP各自与基础转录因子TBP相互作用并共定位于核亚结构，基础转录因子TBP参与这些转录因子和辅因子的激活。将通过检查激酶调节GH启动子激活所需的C/EBPalpha、CBP、Pit-1和TBP活性、这些因子的核定位以及这些因子之间的物理相互作用来评估协同作用的分子基础。 我们已经开发了一系列创新的体内细胞测定，这将使我们能够确定：1。C/EBPalpha和CBP中的结构影响GH启动子的激酶调节的协同激活，2. 激酶调节的C/EBPalpha、CBP和Pit-1 GH启动子激活所需的TBP结构，3. C/EBPalpha、CBP、Pit-1、TBP和TFIIB的核定位以及在功能测定中使用的相同细胞条件下这些因子之间相互作用的时空关系。 4. C/EBPalpha在出生后不久死亡的C/EBPalpha敲除小鼠中GH基因转录的胚胎启动中的作用。

Growth hormone (GH) is a powerful regulator of linear growth and metabolic homeostasis that acts at almost all organ systems. Exogenous GH therapy is costly but effective at counteracting the profound metabolic effects associated with idiopathic GH-deficiency and, seemingly, the normal age-related decline in GH gene transcription. GH synthesis is restricted to the somatotroph cells of the anterior pituitary gland where the transcription of the GH gene is tightly regulated in distinct physiologic, age-related and circadian patterns by systemic and hypothalamic hormones, many of which operate via protein kinase systems. Our long-term goal is to identify the molecular mechanisms of hormone- regulated, somatotroph-specific GH gene expression as a first step in the design of cost-effective therapies targeting GH transcription. The transcription factor C/EBPalpha cooperates with the pituitary-specific transcription factor Pit-1 and the coactivator CBP to control protein kinase A and C-regulated GH gene transcription. Cooperative activation likely arises from mutual or complementary, kinase-regulated actions of C/EBPalpha, Pit-1 and CBP at specific basal factor and/or structural targets. C/EBPalpha, Pit-1 and CBP each interact with, and colocalize to a nuclear substructure with, the basal transcription factor TBP that participates in activation by those transcription factors and cofactor. The molecular basis for cooperative action will be assessed by examining C/EBPalpha, CBP, Pit-1, and TBP activities required for kinase-regulated GH promoter activation by, nuclear localization of, and physical interactions between, those factors. We have already developed a series of innovative in vivo cellular assays which will allow us to determine the: 1. structures in C/EBPalpha and CBP affecting kinase-regulated cooperative activation of the GH promoter, 2. structures in TBP required for kinase-regulated C/EBPalpha, CBP and Pit-1 GH promoter activation, 3. nuclear positioning of C/EBPalpha, CBP, Pit-1, TBP and TFIIB and the spatiotemporal relationships of interactions between those factors under the same cellular conditions used in the functional assays. 4. the role of C/EBPalpha in the embryonic onset of GH gene transcription in C/EBPalpha knockout mice which die shortly after birth.