Schreiber E, Tobler A, Malipiero U, Schaffner W, Fontana A
University Hospital Zurich, Department of Internal Medicine, Switzerland.
Nucleic Acids Res. 1993 Jan 25;21(2):253-8. doi: 10.1093/nar/21.2.253.
Octamer transcription factors (Oct or OTF) are a subset of the POU family of transcription factors which regulate transcription of cellular and viral genes by binding to the octamer sequence motif ATGCAAAT. Neurons and astroglial cells harbour, in addition to the ubiquitous Oct 1 factor, at least four specific factors termed N-Oct 2,3,4 and 5. Here we report the cloning of a human brain-derived cDNA that encodes the N-Oct 3 protein (443 aa) which is the human counterpart of the murine brain-2 gene product. Extracts from mammalian cells transfected with an N-Oct 3 expression vector yield three octamer DNA binding complexes in the electrophoretic mobility shift assay (EMSA): N-Oct 3 and two smaller complexes comigrating with the N-Oct 5A and 5B proteins of brain extracts. We present data suggesting that the N-Oct 5A and 5B proteins are generated by alternative translation initiation at internal AUG residues which are located before the POU domain. In contrast to the putative N-Oct 5 proteins, which are transcriptionally inert, the N-Oct 3 protein activates transcription from a reporter gene promoter with an octamer sequence, when transiently expressed in HeLa cells.
八聚体转录因子（Oct或OTF）是POU转录因子家族的一个子集，通过与八聚体序列基序ATGCAAAT结合来调节细胞和病毒基因的转录。除了普遍存在的Oct 1因子外，神经元和星形胶质细胞还含有至少四种特定因子，称为N-Oct 2、3、4和5。在此，我们报告了一个源自人脑的cDNA的克隆，该cDNA编码N-Oct 3蛋白（443个氨基酸），它是鼠脑-2基因产物的人类对应物。用N-Oct 3表达载体转染的哺乳动物细胞提取物在电泳迁移率变动分析（EMSA）中产生三种八聚体DNA结合复合物：N-Oct 3以及两种与脑提取物中的N-Oct 5A和5B蛋白共迁移的较小复合物。我们提供的数据表明，N-Oct 5A和5B蛋白是由位于POU结构域之前的内部AUG残基处的可变翻译起始产生的。与假定的转录无活性的N-Oct 5蛋白相反，当在HeLa细胞中瞬时表达时，N-Oct 3蛋白可激活具有八聚体序列的报告基因启动子的转录。
