Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea.
Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea.
Biochim Biophys Acta Gene Regul Mech. 2017 Apr;1860(4):416-426. doi: 10.1016/j.bbagrm.2017.01.013. Epub 2017 Feb 1.
CTCF sites (binding motifs for CCCTC-binding factor, an insulator protein) are located considerable distances apart on genomes but are closely positioned in organized chromatin. The close positioning of CTCF sites is often cell type or tissue specific. Here we analyzed chromatin organization in eight CTCF sites around the β-globin locus by 3C assay and explored the roles of erythroid specific transcription activator GATA-1 and KLF1 in it. It was found five CTCF sites convergent to the locus interact with each other in erythroid K562 cells but not in non-erythroid 293 cells. The interaction was decreased by depletion of GATA-1 or KLF1. It accompanied reductions of CTCF and Rad21 occupancies and loss of active chromatin structure at the CTCF sites. Furthermore Rad21 occupancy was reduced in the β-globin locus control region (LCR) hypersensitive sites (HSs) by the depletion of GATA-1 or KLF1. The role of GATA-1 in interaction between CTCF sites was revealed by its ectopic expression in 293 cells and by deletion of a GATA-1 site in the LCR HS2. These findings indicate that erythroid specific activator GATA-1 acts at CTCF sites around the β-globin locus to establish tissue-specific chromatin organization.
CTCF 结合位点（结合因子 CCCTC 结合因子的结合基序，一种绝缘子蛋白）在基因组上彼此相距甚远，但在组织化染色质中紧密排列。CTCF 结合位点的紧密定位通常是细胞类型或组织特异性的。在这里，我们通过 3C 分析分析了β-珠蛋白基因座周围的八个 CTCF 结合位点的染色质组织，并探讨了红细胞特异性转录激活因子 GATA-1 和 KLF1 在其中的作用。结果发现，在红细胞 K562 细胞中，五个会聚到该基因座的 CTCF 结合位点相互作用，但在非红细胞 293 细胞中不相互作用。GATA-1 或 KLF1 的耗竭降低了相互作用。它伴随着 CTCF 和 Rad21 占有率的降低以及 CTCF 结合位点处活性染色质结构的丧失。此外，通过 GATA-1 或 KLF1 的耗竭，Rad21 占有率在β-珠蛋白基因座控制区（LCR）高敏感位点（HS）中降低。GATA-1 在 CTCF 结合位点之间相互作用中的作用是通过其在 293 细胞中的异位表达以及 LCR HS2 中 GATA-1 结合位点的缺失来揭示的。这些发现表明，红细胞特异性激活因子 GATA-1 在β-珠蛋白基因座周围的 CTCF 结合位点上发挥作用，以建立组织特异性染色质组织。
