Brand Marjorie, Ranish Jeffrey A, Kummer Nicolas T, Hamilton Joan, Igarashi Kazuhiko, Francastel Claire, Chi Tian H, Crabtree Gerald R, Aebersold Ruedi, Groudine Mark
Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
Nat Struct Mol Biol. 2004 Jan;11(1):73-80. doi: 10.1038/nsmb713. Epub 2003 Dec 29.
During erythroid differentiation, beta-globin gene expression is regulated by the locus control region (LCR). The transcription factor NF-E2p18/MafK binds within this region and is essential for beta-globin expression in murine erythroleukemia (MEL) cells. Here we use the isotope-coded affinity tag (ICAT) technique of quantitative mass spectrometry to compare proteins interacting with NF-E2p18/MafK during differentiation. Our results define MafK as a 'dual-function' molecule that shifts from a repressive to an activating mode during erythroid differentiation. The exchange of MafK dimerization partner from Bach1 to NF-E2p45 is a key step in the switch from the repressed to the active state. This shift is associated with changes in the interaction of MafK with co-repressors and co-activators. Thus, our results suggest that in addition to its role as a cis-acting activator of beta-globin gene expression in differentiated erythroid cells, the LCR also promotes an active repression of beta-globin transcription in committed cells before terminal differentiation.
在红系分化过程中，β-珠蛋白基因的表达受基因座控制区（LCR）调控。转录因子NF-E2p18/MafK结合于该区域内，对小鼠红白血病（MEL）细胞中的β-珠蛋白表达至关重要。在此，我们运用定量质谱分析的同位素编码亲和标签（ICAT）技术，比较分化过程中与NF-E2p18/MafK相互作用的蛋白质。我们的结果将MafK定义为一种“双功能”分子，其在红系分化过程中从抑制模式转变为激活模式。MafK二聚化伴侣从Bach1交换为NF-E2p45是从抑制状态转变为激活状态的关键步骤。这种转变与MafK与共抑制因子和共激活因子相互作用的变化相关。因此，我们的结果表明，除了在分化的红系细胞中作为β-珠蛋白基因表达的顺式作用激活因子发挥作用外，LCR还在终末分化前促进定向细胞中β-珠蛋白转录的主动抑制。
