Imhof A, Schuierer M, Werner O, Moser M, Roth C, Bauer R, Buettner R
Institute for Pathology, University of Regensburg Medical School, D-93042 Regensburg, Germany.
Mol Cell Biol. 1999 Jan;19(1):194-204. doi: 10.1128/MCB.19.1.194.
AP-2 transcription factors have been suggested to exert key regulatory functions in vertebrate embryonic development, in tumorigenicity of various cancer cell types, and in controlling cell cycle and apoptotic effector genes. In this study, we investigated transcriptional regulation of the AP-2alpha gene promoter mediated by an autoregulatory element (referred to as A32) with a core consensus AP-2 binding site at position -336 relative to the mRNA initiation site. AP-2 and multiple different nuclear proteins in HeLa and Neuro2A cell extracts form specific bandshifts with the A32 element. By screening a mouse brain cDNA expression library, we isolated two different cDNAs encoding the transcription factor BTEB-1 and a novel zinc finger protein, AP-2rep. AP-2rep reveals a modular structure with homology to transcription factors of the wt-1/egr-1-family. AP-2rep, BTEB-1, and AP-2 interact in a mutually exclusive manner with overlapping binding sites in the A32 element. Transfection studies revealed that BTEB-1 is a strong activator of AP-2alpha promoter activity, whereas cotransfected AP-2alpha resulted in moderate autoactivation of promoter activity. In contrast, AP-2rep confers strong transcriptional repression to the AP-2alpha gene, and we observed an excellent correlation between induction of AP-2rep mRNA expression and downregulation of AP-2alpha mRNA during development of the kidney. In summary, we have identified multiple transcription factors and cloned from an expression library a novel zinc finger silencing factor, AP-2rep, mediating positive and negative regulation of AP-2alpha expression through a set of overlapping cis-regulatory promoter elements.
AP-2转录因子被认为在脊椎动物胚胎发育、各种癌细胞类型的致瘤性以及控制细胞周期和凋亡效应基因方面发挥关键的调节功能。在本研究中，我们研究了由一个自调控元件（称为A32）介导的AP-2α基因启动子的转录调控，该元件在相对于mRNA起始位点的-336位置具有一个核心共有AP-2结合位点。AP-2与HeLa和Neuro2A细胞提取物中的多种不同核蛋白与A32元件形成特异性的条带迁移。通过筛选小鼠脑cDNA表达文库，我们分离出两个不同的cDNA，分别编码转录因子BTEB-1和一种新型锌指蛋白AP-2rep。AP-2rep显示出与wt-1/egr-1家族转录因子具有同源性的模块化结构。AP-2rep、BTEB-1和AP-2以相互排斥的方式与A32元件中的重叠结合位点相互作用。转染研究表明，BTEB-1是AP-2α启动子活性的强激活剂，而共转染的AP-2α导致启动子活性的适度自激活。相反，AP-2rep对AP-2α基因具有强转录抑制作用，并且我们观察到在肾脏发育过程中AP-2rep mRNA表达的诱导与AP-2α mRNA的下调之间具有良好的相关性。总之，我们鉴定了多种转录因子，并从一个表达文库中克隆了一种新型锌指沉默因子AP-2rep，它通过一组重叠的顺式调控启动子元件介导AP-2α表达的正负调控。
