Pondel M D, Murphy S, Pearson L, Craddock C, Proudfoot N J
Sir William Dunn School of Pathology, Chemical Pathology Unit, Oxford University, United Kingdom.
Proc Natl Acad Sci U S A. 1995 Aug 1;92(16):7237-41. doi: 10.1073/pnas.92.16.7237.
The 5' flanking region of the human alpha-globin gene is highly G + C rich and contains multiple copies of the consensus sequence for the Sp1 binding site. We investigated the role of this G + C-rich region in augmenting alpha-globin promoter activity in the presence of the far-upstream alpha-globin enhancer, HS-40. We show that in transiently transfected erythroid cells, deletion of the alpha-globin G + C-rich 5' flanking region has no effect on alpha-globin promoter activity. However, upon stable integration into chromatin, deletion of this region causes a nearly 90% decrease in promoter activity compared with expression from an alpha-globin promoter retaining this region. These results suggest that the alpha-globin G + C-rich 5' flanking region augments alpha-globin promoter activity in a chromatin-dependent manner. We further show that this G + C-rich region is required for the activation of alpha-globin gene expression during erythroid differentiation. Finally, we show by both footprint analysis and functional assays that the ability of the G + C-rich region to increase alpha-globin promoter activity from a stably integrated alpha-globin gene is mediated by its multiple binding sites for the transcription factor Sp1.
人类α-珠蛋白基因的5'侧翼区域富含G + C，并包含多个Sp1结合位点的共有序列拷贝。我们研究了这个富含G + C的区域在远上游α-珠蛋白增强子HS-40存在的情况下增强α-珠蛋白启动子活性中的作用。我们发现，在瞬时转染的红系细胞中，α-珠蛋白富含G + C的5'侧翼区域的缺失对α-珠蛋白启动子活性没有影响。然而，在稳定整合到染色质后，与保留该区域的α-珠蛋白启动子的表达相比，该区域的缺失导致启动子活性降低近90%。这些结果表明，α-珠蛋白富含G + C的5'侧翼区域以染色质依赖的方式增强α-珠蛋白启动子活性。我们进一步表明，这个富含G + C的区域是红系分化过程中α-珠蛋白基因表达激活所必需的。最后，我们通过足迹分析和功能测定表明，富含G + C的区域从稳定整合的α-珠蛋白基因增加α-珠蛋白启动子活性的能力是由其多个转录因子Sp1结合位点介导的。
