LEF-1 CONTAINS AN ACTIVATION DOMAIN THAT STIMULATES TRANSCRIPTION ONLY IN A SPECIFIC CONTEXT OF FACTOR-BINDING SITES
LEF-1 CONTAINS AN ACTIVATION DOMAIN THAT STIMULATES TRANSCRIPTION ONLY IN A SPECIFIC CONTEXT OF FACTOR-BINDING SITES
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DOI：
10.1002/j.1460-2075.1993.tb06155.x
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发表时间：
1993-12-01
期刊：
影响因子：
11.4
通讯作者：
GROSSCHEDL, R
中科院分区：
文献类型：
--
作者：
GIESE, K;GROSSCHEDL, R
淋巴细胞增强因子1 （LEF-1）是高迁移基团（HMG）蛋白家族的一员，参与T细胞受体(TCR) α增强子的调控。我们之前已经证明，DNA结合由LEF-1的HMG结构域诱导DNA螺旋的急剧弯曲。再加上LEF-1依赖其他因子结合位点来调节基因表达，HMG结构域诱导的DNA弯曲表明LEF-1具有“建筑”作用。在本研究中，我们进行了实验，以区分HMG结构域是LEF-1唯一功能决定因素的模型和其他LEF-1结构域参与基因表达调控的模型。首先，我们发现单独的HMG结构域不足以刺激TCRalpha增强子的功能。其次，我们将LEF-1的HMG结构域替换为细菌抑制因子LexA的DNA结合结构域，该结构域结合特定的核苷酸序列而不会引起DNA螺旋的急剧弯曲。嵌合LEF-LexA蛋白增加了TCRalpha增强子的活性，其中lef -1结合位点被LexA识别序列取代。然而，LEF-LexA的转录刺激效果不如内源性LEF-1。lef - lexa介导的基因表达激活依赖于LEF-1的氨基末端区域和TCRalpha增强子中因子结合位点的特定背景。无论是多聚化的lexa结合位点，还是改变因子结合位点空间排列的TCRalpha增强子，都不具有LEF-LexA调控的功能。总之，这些数据表明，LEF-1中的氨基末端区域有助于LEF-1对TCRalpha增强子的上下文依赖性调节，可能是通过与其他增强子结合的蛋白相互作用。
Lymphoid enhancer factor 1 (LEF-1) is a member of the high mobility group (HMG) family of proteins and participates in the regulation of the T cell receptor (TCR) alpha enhancer. We have previously shown that DNA binding by the HMG domain of LEF-1 induces a sharp bend in the DNA helix. Together with the dependence of LEF-1 on other factor-binding sites to regulate gene expression, DNA bending induced by the HMG domain suggested an 'architectural' role for LEF-1. In this study, we performed experiments to distinguish between a model in which the HMG domain is the only functional determinant of LEF-1 and a model in which additional domains of LEF-1 are involved in the regulation of gene expression. First, we show that the HMG domain alone is not sufficient to stimulate TCRalpha enhancer function. Second, we replaced the HMG domain of LEF-1 with the DNA-binding domain of the bacterial repressor LexA, which binds a specific nucleotide sequence without inducing a sharp bend in the DNA helix. The chimeric LEF-LexA protein increased the activity of a TCRalpha enhancer in which the LEF-1-binding site had been replaced with a LexA recognition sequence. Transcriptional stimulation by LEF-LexA, however, was less efficient than that observed with endogenous LEF-1. The LEF-LexA-mediated activation of gene expression was dependent upon an amino-terminal region of LEF-1 and a specific context of factor-binding sites in the TCRalpha enhancer. Neither multimerized LexA-binding sites, nor TCRalpha enhancers with altered spatial arrangements of factor-binding sites, were functional for regulation by LEF-LexA. Together, these data suggest that an amino-terminal region in LEF-1 contributes to the context-dependent regulation of the TCRalpha enhancer by LEF-1, presumably by interacting with other enhancer-bound proteins.