Id (Inhibitor of Differentiation) proteins belong to a family of transcriptional modulators that are characterized by a helix loop helix (HLH) region but lack the basic amino acid domain. Id proteins are known to interact with basic helix-loop-helix (bHLH) transcription factors and function as their negative regulators. The negative role of Id proteins has been well demonstrated in muscle development and some in neuronal cells. In this study, we investigated the effect of Id on the function of BETA2/NeuroD, a bHLH transcription factor responsible for neuron and endocrine cell specific gene expression. cDNAs of several Id isoforms were isolated by yeast two-hybrid system using the bHLH domain of E47, a ubiquitous bHLH partner as a bait. Id proteins expressed in COS M6 cells, were found in both cytosolic and nuclear fractions. Electrophoretic mobility shift assay showed that coexpression of Id2 proteins inhibited BETA2/ NeuroD binding to its target sequence, E-box. Id2 inhibited E-box mediated gene expression in a dose dependent manner in BETA2/NeuroD expressing HIT cells. Id coexpressed with BETA2/NeuroD in HeLa cells, inhibited the stimulatory activity of BETA2/NeuroD. These results suggest that Id proteins may negatively regulate tissue specific gene expression induced by BETA2/NeuroD in neuroendocrine cells and the inhibitory role of Id proteins during differentiation may be conserved in various tissues.

中文翻译：

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Id2 对 BETA2/NeuroD 的抑制。

Id（分化抑制剂）蛋白属于转录调节剂家族，其特征在于螺旋环螺旋 (HLH) 区域但缺乏碱性氨基酸结构域。已知Id蛋白与碱性螺旋-环-螺旋(bHLH)转录因子相互作用并作为它们的负调节因子起作用。Id 蛋白在肌肉发育和一些神经元细胞中的负面作用已得到充分证明。在这项研究中，我们研究了 Id 对 BETA2/NeuroD 功能的影响，BETA2/NeuroD 是一种负责神经元和内分泌细胞特异性基因表达的 bHLH 转录因子。使用 E47 的 bHLH 结构域（一种普遍存在的 bHLH 伴侣作为诱饵），通过酵母双杂交系统分离了几种 Id 同种型的 cDNA。在 COS M6 细胞中表达的 Id 蛋白在细胞质和细胞核组分中均有发现。电泳迁移率变化分析表明，Id2 蛋白的共表达抑制了 BETA2/NeuroD 与其靶序列 E-box 的结合。在表达 BETA2/NeuroD 的 HIT 细胞中，Id2 以剂量依赖性方式抑制 E-box 介导的基因表达。Id 在 HeLa 细胞中与 BETA2/NeuroD 共表达，抑制 BETA2/NeuroD 的刺激活性。这些结果表明，Id 蛋白可能对神经内分泌细胞中由 BETA2/NeuroD 诱导的组织特异性基因表达负调控，并且 Id 蛋白在分化过程中的抑制作用在各种组织中可能是保守的。Id 在 HeLa 细胞中与 BETA2/NeuroD 共表达，抑制 BETA2/NeuroD 的刺激活性。这些结果表明，Id 蛋白可能对神经内分泌细胞中由 BETA2/NeuroD 诱导的组织特异性基因表达负调控，并且 Id 蛋白在分化过程中的抑制作用在各种组织中可能是保守的。Id 在 HeLa 细胞中与 BETA2/NeuroD 共表达，抑制 BETA2/NeuroD 的刺激活性。这些结果表明，Id 蛋白可能对神经内分泌细胞中由 BETA2/NeuroD 诱导的组织特异性基因表达负调控，并且 Id 蛋白在分化过程中的抑制作用在各种组织中可能是保守的。