Ye J, Zhang X, Dong Z
Laboratory of Experimental Immunology, DCT, National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702, USA.
Mol Cell Biol. 1996 Jan;16(1):157-67. doi: 10.1128/MCB.16.1.157.
It is well documented that a repeated CATT element in the human granulocyte-macrophage colony-stimulating factor (GM-CSF) gene promoter is required for promoter activity. However, the transcription factors that are able to transactivate this enhancer element remain unidentified. Recently, we have found that nuclear factor YY1 can interact with the enhancer element. Here, we report that in addition to YY1, two other nuclear factors have been identified in the DNA-protein complexes formed by the CATT oligonucleotide and the Jurkat T-cell nuclear protein. One of these factors is AP1, and the other one is an Sp1-related protein. Results from transient transfection of Jurkat T cells have revealed that formation of both AP1 and the Sp1-related complex is required for the full enhancer activity of the CATT element. This result is supported by cotransfection of a c-jun expression vector and mutational analysis of the AP1 site or the Sp1-related protein binding site. In contrast, formation of the YY1 complex suppresses enhancer activity, since deletion of the YY1 complex induces an augmentation of the enhancer activity and overexpression of YY1 results in an attenuation of the enhancer activity. Results from the mechanism study have revealed that YY1 is able to inhibit transactivation mediated by either AP1 or the Sp1-related protein, and YY1 suppressive activity is DNA binding dependent. Taken together, these data support the ideas that AP1 and the Sp1-related nuclear protein are required for transactivation of the human GM-CSF gene promoter and that YY1 can suppress transactivation of the promoter even under inducible conditions.
有充分文献记载，人类粒细胞巨噬细胞集落刺激因子（GM-CSF）基因启动子中重复的CATT元件是启动子活性所必需的。然而，能够反式激活该增强子元件的转录因子仍未明确。最近，我们发现核因子YY1能够与该增强子元件相互作用。在此，我们报告，除了YY1之外，在由CATT寡核苷酸和Jurkat T细胞核蛋白形成的DNA-蛋白质复合物中还鉴定出另外两种核因子。其中一种因子是AP1，另一种是与Sp1相关的蛋白。Jurkat T细胞瞬时转染的结果显示，AP1和与Sp1相关的复合物的形成对于CATT元件的完全增强子活性是必需的。这一结果得到了c-jun表达载体的共转染以及AP1位点或与Sp1相关的蛋白结合位点的突变分析的支持。相反，YY1复合物的形成会抑制增强子活性，因为YY1复合物的缺失会导致增强子活性增强，而YY1的过表达会导致增强子活性减弱。机制研究的结果显示，YY1能够抑制由AP1或与Sp1相关的蛋白介导的反式激活，并且YY1的抑制活性依赖于DNA结合。综上所述，这些数据支持以下观点：AP1和与Sp1相关的核蛋白是人类GM-CSF基因启动子反式激活所必需的，并且即使在诱导条件下，YY1也能够抑制该启动子的反式激活。
