Lister J, Forrester W C, Baron M H
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138-2020, USA.
J Biol Chem. 1995 Jul 28;270(30):17939-46. doi: 10.1074/jbc.270.30.17939.
The Id proteins function as negative regulators of basic-helix-loop-helix transcription factors, which play important roles in determination of cell lineage and in tissue-specific differentiation. Down-regulation of Id1 mRNA is associated with dimethyl sulfoxide-induced terminal differentiation of mouse erythroleukemia cells. To examine the significance of Id1 down-regulation in erythroid differentiation, we generated stable mouse erythroleukemia cell lines that constitutively express a "marked" form of the murine Id1 gene. Terminal erythroid differentiation was inhibited in these lines, as indicated by a block in activation of the erythroid-specific genes alpha-globin, beta-globin, and band 3 and continued proliferation in the presence of dimethyl sulfoxide. Interestingly, this block occurred even in the presence of normal levels of the lineage-specific transcription factors GATA-1, NF-E2, and EKLF. Constitutive expression of Id1 did not interfere with DNase I hypersensitivity at site HS2 of the locus control region, expression of the erythropoietin receptor gene, or down-regulation of the endogenous Id1 or c-myc genes. The differentiation block is reversible in these lines and can be rescued by fusion with human erythroleukemia cells. These findings suggest that in vivo, Id1 functions as an antagonist of terminal erythroid differentiation.
Id蛋白作为碱性螺旋-环-螺旋转录因子的负调控因子，在细胞谱系确定和组织特异性分化中发挥重要作用。Id1 mRNA的下调与二甲基亚砜诱导的小鼠红白血病细胞终末分化相关。为了研究Id1下调在红系分化中的意义，我们构建了稳定表达“标记”形式的鼠Id1基因的小鼠红白血病细胞系。这些细胞系中红系终末分化受到抑制，表现为红系特异性基因α-珠蛋白、β-珠蛋白和带3的激活受阻，以及在二甲基亚砜存在下持续增殖。有趣的是，即使在谱系特异性转录因子GATA-1、NF-E2和EKLF水平正常的情况下，这种阻断仍然发生。Id1的组成性表达并不干扰基因座控制区HS2位点的DNase I超敏反应、促红细胞生成素受体基因的表达，或内源性Id1或c-myc基因的下调。这些细胞系中的分化阻断是可逆的，并且可以通过与人红白血病细胞融合来挽救。这些发现表明，在体内，Id1作为红系终末分化的拮抗剂发挥作用。
