Department of Molecular Biology, College of Natural Sciences, Pusan National University, Pusan 609-735, Korea.
Nucleic Acids Res. 2011 Sep 1;39(16):6944-55. doi: 10.1093/nar/gkr253. Epub 2011 May 24.
GATA-1 and NF-E2 are erythroid specific activators that bind to the β-globin locus. To explore the roles of these activators in transcription of the human fetal stage specific γ-globin genes, we reduced GATA-1 and p45/NF-E2 using shRNA in erythroid K562 cells. GATA-1 or p45/NF-E2 knockdown inhibited the transcription of the γ-globin genes, hypersensitive site (HS) formation in the LCR and chromatin loop formation of the β-globin locus, but histone acetylation across the locus was decreased only in the case of GATA-1 knockdown. In p45/NF-E2 knockdown cells, GATA-1 binding was maintained at the LCR HSs and γ-globin promoter, but NF-E2 binding at the LCR HSs was reduced by GATA-1 knockdown regardless of the amount of p45/NF-E2 in K562 cells. These results indicate that histone acetylation is dependent on GATA-1 binding, but the binding of GATA-1 is not sufficient for the γ-globin transcription, HS formation and chromatin loop formation and NF-E2 is required. This idea is supported by the distinctive binding pattern of CBP and Brg1 in the β-globin locus. Furthermore GATA-1-dependent loop formation between HS5 and 3'HS1 suggests correlation between histone modifications and chromatin looping.
GATA-1 和 NF-E2 是红细胞特异性激活物，可与β-珠蛋白基因座结合。为了研究这些激活物在人类胎儿阶段特异性γ-珠蛋白基因转录中的作用，我们使用 shRNA 在红细胞 K562 细胞中减少了 GATA-1 和 p45/NF-E2 的表达。GATA-1 或 p45/NF-E2 的敲低抑制了γ-珠蛋白基因的转录、LCR 中的高敏感位点（HS）形成和β-珠蛋白基因座的染色质环形成，但只有在 GATA-1 敲低的情况下，整个基因座的组蛋白乙酰化才会降低。在 p45/NF-E2 敲低的细胞中，GATA-1 结合在 LCR HSs 和 γ-珠蛋白启动子上得以维持，但无论 K562 细胞中 p45/NF-E2 的数量如何，GATA-1 敲低都会导致 NF-E2 在 LCR HSs 上的结合减少。这些结果表明，组蛋白乙酰化依赖于 GATA-1 的结合，但 GATA-1 的结合不足以进行 γ-珠蛋白转录、HS 形成和染色质环形成，并且需要 NF-E2。这一观点得到了 CBP 和 Brg1 在β-珠蛋白基因座上独特结合模式的支持。此外，HS5 和 3'HS1 之间 GATA-1 依赖性环形成表明组蛋白修饰和染色质环化之间存在相关性。
