Weller P, Bark C, Janson L, Pettersson U
Department of Medical Genetics, Biomedical Center, Uppsala, Sweden.
Genes Dev. 1988 Nov;2(11):1389-99. doi: 10.1101/gad.2.11.1389.
We have investigated the promoter requirements for in vivo transcription of a human U4C snRNA gene following transfection into HeLa cells. Two elements required for maximal U4C transcription were identified. The first, located upstream of -50, provides a basal level of transcription 2-3% of the full activity, and probably corresponds to the previously identified snRNA gene proximal element. The distal element, centered around -220, acts as a transcriptional enhancer and contains motifs for three previously recognized transcription factors: the octamer-binding protein, NF-A, which binds to motifs in the distal elements of other snRNA genes, and two factors not previously shown to be involved in snRNA gene transcription, cAMP response element binding protein (CREB) and AP-2. The octamer and putative AP-2 motifs are required for maximal transcription of the U4C gene. Specific binding of NF-A and CREB to the motifs in the distal element has been shown in vitro by DNase I and DMS methylation protection footprint competition analyses using HeLa nuclear extracts. The presence of a binding motif for the inducible factor CREB, together with the transcriptional requirement for the putative AP-2 motif, suggests a means by which expression of snRNA genes might be regulated.
我们研究了将人U4C snRNA基因转染入HeLa细胞后，其体内转录所需的启动子条件。鉴定出了最大程度U4C转录所需的两个元件。第一个元件位于-50上游，提供的基础转录水平为全活性的2%-3%，可能对应于先前鉴定的snRNA基因近端元件。远端元件以-220为中心，作为转录增强子，包含三个先前已识别的转录因子的基序：八聚体结合蛋白NF-A，它与其他snRNA基因远端元件中的基序结合，以及两个先前未显示参与snRNA基因转录的因子，即环磷酸腺苷反应元件结合蛋白（CREB）和AP-2。八聚体和假定的AP-2基序是U4C基因最大程度转录所必需的。通过使用HeLa细胞核提取物的DNase I和DMS甲基化保护足迹竞争分析，已在体外证明NF-A和CREB与远端元件中的基序特异性结合。诱导因子CREB结合基序的存在，以及假定的AP-2基序的转录需求，提示了一种调节snRNA基因表达的方式。
