Ikuta T, Kan Y W, Swerdlow P S, Faller D V, Perrine S P
Hemoglobinopathy-Thalassemia Research Unit and Cancer Research Center, Departments of Pharmacology and Experimental Therapeutics, Pediatrics, and Medicine, Boston University School of Medicine, Boston, MA, USA.
Blood. 1998 Oct 15;92(8):2924-33.
The mechanisms by which pharmacologic agents stimulate gamma-globin gene expression in beta-globin disorders has not been fully established at the molecular level. In studies described here, nucleated erythroblasts were isolated from patients with beta-globin disorders before and with butyrate therapy, and globin biosynthesis, mRNA, and protein-DNA interactions were examined. Expression of gamma-globin mRNA increased twofold to sixfold above baseline with butyrate therapy in 7 of 8 patients studied. A 15% to 50% increase in gamma-globin protein synthetic levels above baseline gamma globin ratios and a relative decrease in beta-globin biosynthesis were observed in responsive patients. Extensive new in vivo footprints were detected in erythroblasts of responsive patients in four regions of the gamma-globin gene promoter, designated butyrate-response elements gamma 1-4 (BRE-G1-4). Electrophoretic mobility shift assays using BRE-G1 sequences as a probe demonstrated that new binding of two erythroid-specific proteins and one ubiquitous protein, alphaCP2, occurred with treatment in the responsive patients and did not occur in the nonresponder. The BRE-G1 sequence conferred butyrate inducibility in reporter gene assays. These in vivo protein-DNA interactions in human erythroblasts in which gamma-globin gene expression is being altered strongly suggest that nuclear protein binding, including alphaCP2, to the BRE-G1 region of the gamma-globin gene promoter mediates butyrate activity on gamma-globin gene expression.
在β珠蛋白病中，药物刺激γ珠蛋白基因表达的机制在分子水平上尚未完全明确。在本文所述的研究中，从β珠蛋白病患者治疗前及使用丁酸盐治疗时分离出有核红细胞，并检测珠蛋白生物合成、mRNA及蛋白质-DNA相互作用。在8例研究患者中，有7例经丁酸盐治疗后，γ珠蛋白mRNA表达比基线水平增加了2至6倍。在有反应的患者中，观察到γ珠蛋白合成水平比基线γ珠蛋白比例增加了15%至50%，且β珠蛋白生物合成相对减少。在有反应患者的红细胞中，在γ珠蛋白基因启动子的四个区域检测到广泛的新的体内足迹，命名为丁酸盐反应元件γ1-4（BRE-G1-4）。使用BRE-G1序列作为探针的电泳迁移率变动分析表明，在有反应的患者中，两种红系特异性蛋白和一种普遍存在的蛋白αCP2的新结合发生在治疗后，而在无反应者中未发生。在报告基因分析中，BRE-G1序列赋予丁酸盐诱导性。在人红细胞中γ珠蛋白基因表达发生改变的这些体内蛋白质-DNA相互作用强烈提示，包括αCP2在内的核蛋白与γ珠蛋白基因启动子的BRE-G1区域结合介导了丁酸盐对γ珠蛋白基因表达的作用。
