Dissecting molecular steps in chromatin domain activation during hematopoietic differentiation
Dissecting molecular steps in chromatin domain activation during hematopoietic differentiation
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DOI：
10.1128/mcb.00235-07
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发表时间：
2007-06-01
影响因子：
5.3
通讯作者：
Bresnick, Emery H.
中科院分区：
文献类型：
--
作者：
Kim, Shin-Il;Bultman, Scott J.;Bresnick, Emery H.
GATA 因子通过多步骤转录机制协调造血作用，但各个步骤的相互关系和重要性尚不清楚。通过对 GATA-1 缺失细胞和含有染色质重塑蛋白 BRG1 亚等位基因的小鼠进行互补分析，我们剖析了从 GATA-1 结合到辅因子招募、染色质环形成和转录激活的途径。对 GATA-1 介导的 β-珠蛋白位点激活的分析（其中 GATA-1 在启动子和远端位点控制区 (LCR) 处组装分散的复合物）揭示了分子中间体，包括不依赖 GATA-1 和包含 GATA-1 的 LCR 子复合物，它们在促进环形成方面都有缺陷。另一个中间体由明显正常的 LCR 复合物和总 RNA 聚合酶 II (Pol II) 水平降低的启动子复合物组成，并且 Pol II 在羧基末端结构域的丝氨酸 5 处磷酸化。 BRG1 活性降低仅损害启动子处的 Pol II 和丝氨酸 5-磷酸化 Pol II 占据，从而对 LCR 缺失的小鼠进行表型复制。这些研究定义了复杂基因座上 GATA-1 触发事件的层次顺序，并建立了一种新的远程基因调控机制。
GATA factors orchestrate hematopoiesis via multistep transcriptional mechanisms, but the interrelationships and importance of individual steps are poorly understood. Using complementation analysis with GATA-1-null cells and mice containing a hypomorphic allele of the chromatin remodeler BRG1, we dissected the pathway from GATA-1 binding to cofactor recruitment, chromatin loop formation, and transcriptional activation. Analysis of GATA-1-mediated activation of the beta-globin locus, in which GATA-1 assembles dispersed complexes at the promoters and the distal locus control region (LCR), revealed molecular intermediates, including GATA-1-independent and GATA-1-containing LCR subcomplexes, both defective in promoting loop formation. An additional intermediate consisted of an apparently normal LCR complex and a promoter complex with reduced levels of total RNA polymerase II (Pol II) and Pol II phosphorylated at serine 5 of the carboxy-terminal domain. Reduced BRG1 activity solely compromised Pol II and serine 5-phosphorylated Pol II occupancy at the promoter, phenocopying the LCR-deleted mouse. These studies defined a hierarchical order of GATA-1-triggered events at a complex locus and establish a novel mechanism of long-range gene regulation.