CHROMATIN STRUCTURE IN REGULATION OF MAMMALIAN GENE EXPRESSION

编码组织和发育的真核基因的转录 阶段特异性蛋白质是一个复杂的过程，涉及相互作用 核染色质与RNA聚合酶II以及其他 转录调控因子。珠蛋白的个别成员 基因家族在时间上受到调节，从而导致序列 胚胎、胎儿和成人血红蛋白在红系中的表达 许多物种的组织。对这些基因的研究在很大程度上有助于 我们对选择性转录是如何完成的理解。这个 Epsilon-珠蛋白基因是贝塔类珠蛋白基因中的第一个 在人类发展过程中表现出来的。调查这方面的监管情况 我们已经在体外定位了核之间相互作用的部位 来自红系和非红系细胞的蛋白质和DNA序列 Epsilon-珠蛋白启动子。我们发现红系因子GATA-1结合 与启动子中的三个位点，以及包括SP-1在内的其他因子结合 到CACCC和CCAAT网站。在瞬变中使用CAT报告器构造 表达分析，我们发现GATA-1位点在-165位是 两种红系特异性增强子的转录增强作用。此站点 在哺乳动物胚胎珠蛋白的进化过程中是保守的 基因。每个增强子都含有它们自己的结合位点。 对于强调模块化性质的核蛋白(通常是相同的) 转录调控区域。在每一种情况下，积极的行为 增强子的区域由AP-1基序组成。因此，多产 启动子-增强子相互作用促进ETA-珠蛋白转录 基因可能只需要两个蛋白质通过两个调控因子相互作用 DNA中的位置。

The transcription of eukaryotic genes encoding tissue and developmental stage specific proteins is a complex process involving the interaction of nuclear chromatin with RNA polymerase II, as well as with other transcriptional regulatory factors. The individual members of the globin gene family are temporally regulated to bring about the sequential expression of embryonic, fetal, and adult hemoglobins in the erythroid tissues of many species. The study of these genes has contributed much to our understanding of how selective transcription is accomplished. The epsilon-globin gene is the first of the betalike globin genes to be expressed during human development. To investigate the regulation of this gene we have mapped, in vitro , the sites of interaction between nuclear proteins from erythroid and non-erythroid cells, and DNA sequences in the epsilon-globin promoter. We found that the erythroid factor GATA- 1 bound to three sites in the promoter, and other factors, including SP- 1, bound to the CACCC and CCAAT sites. Using a CAT reporter construct in transient expression assays, we found that the GATA-1 site at -165 is required for transcriptional enhancement by two erythroid specific enhancers. This site has been conserved during the evolution of the mammalian embryonic globin genes. The enhancers each contain their own complement of binding sites for (often the same) nuclear proteins emphasizing the modular nature of transcriptional regulatory regions. In each case the positive-acting regions of the enhancers consisted of AP-1 motifs. Thus, productive promoter-enhancer interactions increasing transcription of the eta-globin gene may require as few as two proteins interacting through two regulatory sites in the DNA.