Identification and functional analysis of erythroid-specific genes regulated by heme

红系细胞在其分化的后期合成并积累大量血红蛋白。这是可能的，除了血红蛋白的合成，血红素也可能发挥另一个重要的作用，在红细胞分化程序。为了鉴定红系特异性血红素调节基因，我们在野生型和血红素缺陷型成红细胞之间进行了差异表达分析，所述成红细胞分别从野生型和δ-氨基乙酰丙酸合酶（ALAS 2）缺失的小鼠ES细胞制备。因此，最后4个被认为是新鉴定的红系特异性血红素调节基因。这4个基因分别是解偶联蛋白2（UCP 2）、核仁纺锤体相关蛋白（NuSAP）、细胞核酸结合蛋白（CNBP）和一种新的乙酰转移酶样蛋白。其中，对Nusap的功能作了进一步的分析。NuSAP mRNA在未成熟成红细胞亚群（TER 119 ^+ CD 71 ^）中的丰度明显高于成熟<high>成红细胞亚群（TER 119 ^+ CD 7 ^<low>），并且在体内放血小鼠的TER 119 ^+细胞中显著增加。提示NuSAP基因可能参与了未成熟成红细胞池的扩增。因此，这些研究结果表明，血红素可以调节红系细胞分化的各种基因。

Erythroid cells synthesize and accumulate an enormous amount of hemoglobin in the late stage of their differentiation. It is possible that, in addition to hemoglobin synthesis, heme may also play another important role in the erythroid cell differentiation program. To identify erythroid- specific heme-regulated genes, we performed differential expression analysis between wild-type and heme-deficient erythroblasts, which had been prepared from wild-type and δ-aminolevulinate synthase (ALAS2)-null mouse ES cells, respectively. As a result, the final 4 were considered as the newly identified erythroid-specific heme-regulated genes. These 4 genes were uncoupling protein 2 (UCP2), nucleolar spindle-associated protein (NuSAP), cellular nucleic acid binding protein (CNBP), and a novel acetyltransferase-like protein. Among them, the function of Nusap was further analyzed. NuSAP mRNA was remarkably more abundant in the subset corresponding to immature erythroblasts (TER119^+CD71^<high>) than mature erythroblasts (TER119^+CD7^<low>), and it was significantly increased in TER119^+ cells from in vivo phlebotomized mice. These results suggested that NuSAP gene might contribute to the expansion of immature erythroblast pool. These findings thus suggest that heme may regulate a wide variety of genes in erythroid cell differentiation.