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首页> 外文期刊>Molecular and Cellular Biology >Interaction of several related GC-box- and GT-box-binding proteins with the intronic enhancer is required for differential expression of the gb110 gene in embryonal carcinoma cells.
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Interaction of several related GC-box- and GT-box-binding proteins with the intronic enhancer is required for differential expression of the gb110 gene in embryonal carcinoma cells.

机译：gb110基因在胚胎癌细胞中的差异表达需要几种相关的GC-box-box和GT-box-bind结合蛋白与内含子增强子的相互作用。

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The molecular mechanisms by which expression of a gene is down-regulated after differentiation of F9 embryonal carcinoma cells into parietal endoderm-like cells was studied by characterizing the cis- and trans-regulatory elements of the gb110 gene. This gene encodes a putative RNA helicase, and its expression is down-regulated when F9 cells are differentiated with retinoic acid and cyclic AMP. The 5'-flanking region of the gene has all of the features of a GC-rich island promoter and seems to play only a minor role, if any, in the regulated expression. A 133-bp enhancer in the first intron was identified by transient chloramphenicol acetyltransferase assays that activated expression in undifferentiated F9 cells about 50- to 100-fold. As this enhancer was not active in differentiated F9 cells, it seems to be the prime mediator of the differentiation-specific down-regulation of the gb110 gene. Four different protein-binding sites, three of which contain GC- and GT-box motifs, were identified in the enhancer element. The fourth site, interacting with previously described transcription factor FTZ-F1/ELP, seems to be of minor importance for the activity of the enhancer. Mutational analysis showed that the cooperative interaction of several most likely related proteins with the three GC- and GT-box motifs was required for full enhancer activity. On the basis of their binding properties, at least two of these proteins seem to be identical or closely related to ubiquitous transcription factor Sp1. One of the GT-box-binding proteins was present in undifferentiated F9 cells but not, however, in its differentiated derivatives. The cell specificity of this transcription factor explains why the gb110 gene is not expressed or expressed only at low levels in parietal endoderm-like cells.
机译：通过表征gb110基因的顺式和反式调控元件，研究了F9胚胎癌细胞分化为壁内胚层样细胞后基因表达下调的分子机制。该基因编码推定的RNA解旋酶，当用视黄酸和环状AMP分化F9细胞时，其表达下调。该基因的5'侧翼区域具有富含GC的岛启动子的所有特征，并且似乎在调节表达中仅起次要作用。通过瞬时氯霉素乙酰转移酶测定法鉴定了第一个内含子中的133 bp增强子，该测定法激活了未分化F9细胞中约50至100倍的表达。由于这种增强子在分化的F9细胞中没有活性，因此它似乎是gb110基因分化特异性下调的主要介体。在增强子元件中鉴定出四个不同的蛋白质结合位点，其中三个含有GC-和GT-box基序。与先前描述的转录因子FTZ-F1 / ELP相互作用的第四个位点似乎对增强子的活性次要。突变分析表明，几种最可能相关的蛋白质与三个GC-box和GT-box-基序的协同相互作用是增强剂充分发挥作用所必需的。基于它们的结合特性，这些蛋白质中的至少两个似乎与普遍存在的转录因子Sp1相同或紧密相关。 GT-box结合蛋白之一存在于未分化的F9细胞中，但不存在于其分化衍生物中。该转录因子的细胞特异性解释了为什么gb110基因在顶壁内胚层样细胞中不表达或仅以低水平表达。

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