Schreiber E, Harshman K, Kemler I, Malipiero U, Schaffner W, Fontana A
Institut für Molekularbiologie II, Universität Zürich, Switzerland.
Nucleic Acids Res. 1990 Sep 25;18(18):5495-503. doi: 10.1093/nar/18.18.5495.
The 'octamer' sequence, ATGCAAAT or its complement ATTTGCAT, is a key element for the transcriptional regulation of immunoglobulin genes in B-lymphocytes as well as a number of housekeeping genes in all cell types. In lymphocytes, the octamer-binding protein Oct-2A and variants thereof are thought to contribute to the B-cell specific gene expression, while the ubiquitous protein Oct-1 seems to control general octamer site-dependent transcription. Various other genes, for example interleukin-1 and MHC class II genes, contain an octamer sequence in the promoter and are expressed in cells of both the immune and nervous systems. This prompted us to analyze the octamer-binding proteins in the latter cells. Using the electrophoretic mobility shift assay, at least six novel octamer binding proteins were detected in nuclear extracts of cultured mouse astrocytes. These proteins are differentially expressed in human glioblastoma and neuroblastoma cell lines. The nervous system-derived (N-Oct) proteins bound to the octamer DNA sequence in a manner which is indistinguishable from the Oct-1 and Oct-2A proteins. The relationship of the N-Oct proteins to Oct-1 and Oct-2A was analyzed by proteolytic clipping bandshift assays and by their reactivity towards antisera raised against recombinant Oct-1 and Oct-2A proteins. On the basis of these assays, all N-Oct-factors were found to be distinct from the ubiquitous Oct-1 and the lymphoid-specific Oct-2A proteins. In melanoma cells that contain the N-Oct-3 factor, a transfected lymphocyte-specific promoter was neither activated nor was it repressed upon contransfection with an Oct-2A expression vector. We therefore speculate that N-Oct-3 and other N-Oct factors have a specific role in gene expression in cells of the nervous system.
“八聚体”序列ATGCAAAT或其互补序列ATTTGCAT，是B淋巴细胞中免疫球蛋白基因以及所有细胞类型中许多管家基因转录调控的关键元件。在淋巴细胞中，八聚体结合蛋白Oct-2A及其变体被认为有助于B细胞特异性基因表达，而普遍存在的蛋白Oct-1似乎控制着一般的八聚体位点依赖性转录。其他各种基因，例如白细胞介素-1和MHC II类基因，在启动子中含有八聚体序列，并在免疫和神经系统的细胞中表达。这促使我们分析后一种细胞中的八聚体结合蛋白。使用电泳迁移率变动分析，在培养的小鼠星形胶质细胞核提取物中检测到至少六种新的八聚体结合蛋白。这些蛋白在人胶质母细胞瘤和神经母细胞瘤细胞系中差异表达。神经系统来源的（N-Oct）蛋白以与Oct-1和Oct-2A蛋白无法区分的方式与八聚体DNA序列结合。通过蛋白水解剪切带移分析及其对针对重组Oct-1和Oct-2A蛋白产生的抗血清的反应性，分析了N-Oct蛋白与Oct-1和Oct-2A的关系。基于这些分析，发现所有N-Oct因子都与普遍存在的Oct-1和淋巴样特异性Oct-2A蛋白不同。在含有N-Oct-3因子的黑色素瘤细胞中，转染的淋巴细胞特异性启动子在与Oct-2A表达载体共转染时既未被激活也未被抑制。因此，我们推测N-Oct-3和其他N-Oct因子在神经系统细胞的基因表达中具有特定作用。
