Transcriptional regulation of the murine erythroid-specific 5-aminolevulinate synthase gene
Transcriptional regulation of the murine erythroid-specific 5-aminolevulinate synthase gene
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DOI：
10.1016/s0378-1119(00)00103-7
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发表时间：
2000-04-18
期刊：
影响因子：
3.5
通讯作者：
Ferreira, GC
中科院分区：
文献类型：
--
作者：
Kramer, MF;Gunaratne, P;Ferreira, GC
5-氨基乙酰丙酸合酶 (ALAS) 催化哺乳动物细胞中血红素生物合成途径的第一步。不同的基因编码两种亚型：普遍表达的 ALAS (ALAS1) 和红细胞特异性 ALAS (ALAS2)。 ALAS2 基因的转录仅在红细胞分化过程中被激活。这种刺激可以形成血红蛋白特异性血红素。研究了小鼠 ALAS2 基因的 5' 侧翼区域，以确定其在转录激活中的红细胞特异性功能。在小鼠 ALAS2 5' 侧翼区域的前 300 bp 区域内鉴定了红细胞特异性核因子 GATA-1、NF-E2 和 EKLF 的推定结合位点。然而，仅这个 300 bp 区域并不能有效激活红系 MEL 和 K562 细胞系中的瞬时表达。转录起始位点上游 300-718 bp 内发现的额外 DNA 调控序列是最大转录激活所必需的，尽管这些区域在非红系 HeLa 和 NIH/3T3 细胞中刺激了类似的表达。这表明 5' 侧翼区域中存在的顺式作用元件不负责维持非红系细胞系中的转录沉默，并且 ALAS2 的组织特异性调节取决于基因的其他区域或染色质重塑。在 300-718 bp 上游区域内鉴定出了假定的缺氧诱导因子 1 (HIF-1) 反应元件。值得注意的是，两个近端 GATA-1 结合位点（-118/-113 和 -98/-93）和位于小鼠 ALAS2 启动子 -518 至 -315 bp 内的区域对于化学诱导 MEL 细胞分化过程中的转录激活至关重要，这意味着它们在赋予 ALAS2 转录激活红细胞特异性方面的重要性。这是第一项界定在 MEL 细胞中二甲基亚砜诱导后负责激活 ALAS2 启动子的顺式作用区域的研究。 (C) 2000 Elsevier Science B.V. 保留所有权利。
5-Aminolevulinate synthase (ALAS) catalyzes the first step of the heme biosynthetic pathway in mammalian cells. Separate genes encode the two isoforms: ubiquitously expressed ALAS (ALAS1) and erythroid-specific ALAS (ALAS2). Transcription of the ALAS2 gene is only activated during erythroid cell differentiation. This stimulation allows for the formation of hemoglobin-specific heme. The 5'-flanking region of the mouse ALAS2 gene was studied in order to define its erythroid-specific function in transcriptional activation. Putative binding sites for the erythroid-specific nuclear factors GATA-1, NF-E2, and EKLF were identified within the first 300 bp region of the mouse ALAS2 5'-flanking region. However, this 300 bp region alone did not efficiently activate transient expression in erythroid MEL and K562 cell lines. Additional DNA regulatory sequences found within 300-718 bp upstream of the transcription start site were required for maximal transcriptional activation, even though these regions stimulated similar expression in the non-erythroid HeLa and NIH/3T3 cells. This suggests that cis-acting elements present in the 5'-flanking region are not responsible for maintenance of transcriptional silencing in non-erythroid cell lines and that tissue-specific regulation of ALAS2 depends on other regions of the gene or on chromatin remodeling. A putative hypoxia inducible factor 1 (HIF-1) response element was identified within the 300-718 bp upstream region. Significantly, two proximal GATA-1-binding sites (-118/-113 and -98/-93) and a region located within -518 to -315 bp of the mouse ALAS2 promoter were essential for transcriptional activation during chemically induced differentiation of MEL cells, implying their importance in conferring erythroid specificity to the ALAS2 transcriptional activation. This is the first study to delimit the cis-acting region responsible for activation of the ALAS2 promoter upon dimethyl-sulfoxide induction in MEL cells. (C) 2000 Elsevier Science B.V. All rights reserved.