Kooren Jurgen, Palstra Robert-Jan, Klous Petra, Splinter Erik, von Lindern Marieke, Grosveld Frank, de Laat Wouter
Department of Cell Biology, Erasmus Medical Center, P. O. Box 2040, 3000 CA Rotterdam, The Netherlands.
J Biol Chem. 2007 Jun 1;282(22):16544-52. doi: 10.1074/jbc.M701159200. Epub 2007 Apr 11.
Expression of the beta-globin genes proceeds from basal to exceptionally high levels during erythroid differentiation in vivo. High expression is dependent on the locus control region (LCR) and coincides with more frequent LCR-gene contacts. These contacts are established in the context of an active chromatin hub (ACH), a spatial chromatin configuration in which the LCR, together with other regulatory sequences, loops toward the active beta-globin-like genes. Here, we used recently established I/11 cells as a model system that faithfully recapitulates the in vivo erythroid differentiation program to study the molecular events that accompany and underlie ACH formation. Upon I/11 cell induction, histone modifications changed, the ACH was formed, and the beta-globin-like genes were transcribed at rates similar to those observed in vivo. The establishment of frequent LCR-gene contacts coincided with a more efficient loading of polymerase onto the beta-globin promoter. Binding of the transcription factors GATA-1 and EKLF to the locus, although previously shown to be required, was not sufficient for ACH formation. Moreover, we used knock-out mice to show that the erythroid transcription factor p45 NF-E2, which has been implicated in beta-globin gene regulation, is dispensable for beta-globin ACH formation.
在体内红系分化过程中，β-珠蛋白基因的表达从基础水平持续上升至极高水平。高表达依赖于基因座控制区（LCR），并与更频繁的LCR-基因接触同时出现。这些接触是在活性染色质枢纽（ACH）的背景下建立的，ACH是一种空间染色质构型，其中LCR与其他调控序列一起向活跃的β-珠蛋白样基因环化。在这里，我们使用最近建立的I/11细胞作为模型系统，该系统忠实地重现了体内红系分化程序，以研究伴随ACH形成并作为其基础的分子事件。在I/11细胞诱导后，组蛋白修饰发生变化，ACH形成，β-珠蛋白样基因以与体内观察到的速率相似的速度转录。频繁的LCR-基因接触的建立与聚合酶更有效地加载到β-珠蛋白启动子上同时发生。转录因子GATA-1和EKLF与该基因座的结合，尽管先前已证明是必需的，但不足以形成ACH。此外，我们使用基因敲除小鼠表明，参与β-珠蛋白基因调控的红系转录因子p45 NF-E2对于β-珠蛋白ACH的形成是可有可无的。
