The β-globin locus control region (LCR) functions primarily by enhancing the transition from transcription initiation to elongation
The β-globin locus control region (LCR) functions primarily by enhancing the transition from transcription initiation to elongation
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DOI：
10.1101/gad.1072303
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发表时间：
2003-04-15
影响因子：
10.5
通讯作者：
Groudine, M
中科院分区：
文献类型：
--
作者：
Sawado, T;Halow, J;Groudine, M
为了研究 P-珠蛋白基因激活的分子基础，我们分析了野生型 (WT)/基因座控制区敲除 (ALCR) 杂合小鼠和鼠红白血病 (MEL) 细胞中成人 P-珠蛋白基因的因子招募和组蛋白修饰。尽管组蛋白乙酰化和甲基化 (Lys 4) 在 MEL 分化之前和之后都很高，但红细胞特异性激活剂 NF-E2 募集到启动子和预启动复合物 (PIC) 组装仅在分化后发生。我们之前报道过，LCR 的靶向删除可将 β-珠蛋白基因表达降低至 WT 的 1%-4%，而不影响启动子组蛋白乙酰化。在这里，我们报告 NF-E2 同样有效地招募到 ALCR 和 WT 等位基因的成年 P-珠蛋白启动子。此外，LCR 缺失仅使 PIC 组装减少两倍，但对 RNA 聚合酶 II 的 Ser 5 磷酸化和转录延伸具有显着影响。我们的结果表明，β-珠蛋白基因激活至少存在三个不同的阶段：（1）在 NF-E2 募集至启动子和 PIC 组装之前的不依赖于 LCR 的染色质开放阶段； (2) NF-E2结合（不依赖LCR）和PIC组装（部分LCR依赖）发生的中间阶段； (3) LCR依赖性完全活性阶段，其特征在于有效的pol II延伸。因此，在其天然位置，LCR 主要在激活剂招募和 PIC 组装的下游发挥作用。
To investigate the molecular basis of P-globin gene activation, we analyzed factor recruitment and histone modification at the adult p-globin gene in wild-type (WT)/locus control region knockout (ALCR) heterozygous mice and in murine erythroleukemia (MEL) cells. Although histone acetylation and methylation (Lys 4) are high before and after MEL differentiation, recruitment of the erythroid-specific activator NF-E2 to the promoter and preinitiation complex (PIC) assembly occur only after differentiation. We reported previously that targeted deletion of the LCR reduces beta-globin gene expression to 1%-4% of WT without affecting promoter histone acetylation. Here, we report that NF-E2 is recruited equally efficiently to the adult P-globin promoters of the ALCR and WT alleles. Moreover, the LCR deletion reduces PIC assembly only twofold, but has a dramatic effect on Ser 5 phosphorylation of RNA polymerase II and transcriptional elongation. Our results suggest at least three distinct stages in beta-globin gene activation: (1) an LCR-independent chromatin opening stage prior to NF-E2 recruitment to the promoter and PIC assembly; (2) an intermediate stage in which NF-E2 binding (LCR-independent) and PIC assembly (partially LCR-dependent) occur; and (3) an LCR-dependent fully active stage characterized by efficient pol II elongation. Thus, in its native location the LCR functions primarily downstream of activator recruitment and PIC assembly.