Chromatin domain activation via GATA-1 utilization of a small subset of dispersed GATA motifs within a broad chromosomal region
Chromatin domain activation via GATA-1 utilization of a small subset of dispersed GATA motifs within a broad chromosomal region
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DOI：
10.1073/pnas.0506164102
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发表时间：
2005-11-22
影响因子：
11.1
通讯作者：
Bresnick, EH
中科院分区：
文献类型：
--
作者：
Im, H;Grass, JA;Bresnick, EH
基因组中有大量的顺式元件介导转录因子的结合，但这些基序在染色质中占据的规则还不清楚。调节红细胞发育的转录因子加塔-1以高亲和力结合加塔基序，并且初步研究表明这些基序通常不能用于染色质中的占据。尽管加塔-2通过加塔基序结合调节所有血细胞谱系的分化，但尚未研究加塔-2染色质占据的特异性。我们发现，条件活性加塔-1（ER-加塔-1）和加塔-2仅占据鼠β-珠蛋白基因座内保守加塔基序的一小部分。在加塔-1-null细胞中的动力学分析表明，ER-加塔-1优先占据基因座控制区（LCR）的加塔基序，其中染色质可及性在很大程度上是加塔-1-独立的。随后，ER-GATA-1增加了启动子的可及性并占据了β主要启动子。ER-GATA-1增加红系Kruppel样因子和SWI/SNF染色质重塑复合物在限制性LCR位点的占有率。这些研究揭示了β-珠蛋白基因座激活的三个阶段：加塔-1-独立的特定染色质结构特征的建立，加塔-1-依赖的LCR复合物组装，和加塔-1-依赖的启动子复合物组装。因此，分散的加塔基序的差异利用建立了空间/时间调节，并成为多步激活机制的基础。
Cis elements that mediate transcription factor binding are abundant within genomes, but the rules governing occupancy of such motifs in chromatin are not understood. The transcription factor GATA-1 that regulates red blood cell development binds with high affinity to GATA motifs, and initial studies suggest that these motifs are often unavailable for occupancy in chromatin. Whereas GATA-2 regulates the differentiation of all blood cell lineages via GATA motif binding, the specificity of GATA-2 chromatin occupancy has not been studied. We found that conditionally active GATA-1 (ER-GATA-1) and GATA-2 occupy only a small subset of the conserved GATA motifs within the murine beta-globin locus. Kinetic analyses in GATA-1-null cells indicated that ER-GATA-1 preferentially occupied GATA motifs at the locus control region (LCR), in which chromatin accessibility is largely GATA-1-independent. Subsequently, ER-GATA-1 increased promoter accessibility and occupied the beta major promoter. ER-GATA-1 increased erythroid Kruppel-like factor and SWI/SNF chromatin remodeling complex occupancy at restricted LCR sites. These studies revealed three phases of beta-globin locus activation: GATA-1-independent establishment of specific chromatin structure features, GATA-1-dependent LCR complex assembly, and GATA-1-dependent promoter complex assembly. The differential utilization of dispersed GATA motifs therefore establishes spatial/temporal regulation and underlies the multistep activation mechanism.