Sun J M, Penner C G, Davie J R
Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Nucleic Acids Res. 1992 Dec 11;20(23):6385-92. doi: 10.1093/nar/20.23.6385.
The chicken erythroid proteins binding to the histone H5 5' promoter and 3' erythroid-specific enhancer regions were identified. In DNase I footprinting and gel mobility shift experiments with immature adult erythrocyte nuclear extracts, we have demonstrated the binding of proteins to the GC-box, a high affinity Sp1 binding site, and to the upstream promoter element. We have previously demonstrated that a multisubunit complex containing the transcription factor GATA-1 was associated with the enhancer. Here, we show that the enhancer region also has four Sp1 binding sites (one medium and three weak affinity, one of which may also bind the CACCC factor), a potential NF-E4 binding site, and a binding site for a NF1-like factor. The results of gel mobility-shift and competition experiments provide evidence that the Sp1 binding sites are associated with a high molecular mass (greater than 450 kDa), Sp1 containing protein complex. We propose that Sp1 multimers bound at the promoter and enhancer interact to mediate the juxta-positioning of the enhancer and promoter elements, bringing the GATA-1 multisubunit complex next to the initiation site. The GATA-1 complex may contribute to the protein-protein interactions between the enhancer and promoter.
已鉴定出与组蛋白H5 5'启动子和3'红细胞特异性增强子区域结合的鸡红细胞蛋白。在用未成熟成年红细胞核提取物进行的DNase I足迹分析和凝胶迁移率变动实验中，我们证明了蛋白质与GC盒（一种高亲和力的Sp1结合位点）以及上游启动子元件的结合。我们之前已经证明，含有转录因子GATA-1的多亚基复合物与增强子相关。在此，我们表明增强子区域还具有四个Sp1结合位点（一个中等亲和力和三个弱亲和力，其中一个也可能结合CACCC因子）、一个潜在的NF-E4结合位点以及一个NF1样因子的结合位点。凝胶迁移率变动和竞争实验的结果提供了证据，表明Sp1结合位点与一种高分子量（大于450 kDa）、含有Sp1的蛋白质复合物相关。我们提出，结合在启动子和增强子上的Sp1多聚体相互作用，介导增强子和启动子元件的并列定位，使GATA-1多亚基复合物靠近起始位点。GATA-1复合物可能有助于增强子和启动子之间的蛋白质-蛋白质相互作用。
