Krasnow M A, Saffman E E, Kornfeld K, Hogness D S
Department of Biochemistry, Stanford University, CA 94305.
Cell. 1989 Jun 16;57(6):1031-43. doi: 10.1016/0092-8674(89)90341-3.
Homeotic genes of Drosophila melanogaster such as Ultrabithorax (Ubx) and Antennapedia (Antp) have long been thought to select metameric identity during development by controlling the expression of various target genes. Here we describe a cotransfection assay in cultured D. melanogaster cells that is used to demonstrate that Ubx proteins (UBX) can repress an Antp promoter fusion and activate a Ubx promoter fusion, activities predicted from genetic studies. We show (a) that UBX proteins regulated the level of accurately initiated Antp P1 and Ubx transcripts, (b) that activation of the Ubx promoter required a downstream cluster of UBX binding sites, and (c) that binding site sequences were sufficient to confer regulation on a heterologous promoter, regardless of their orientation or precise position. We conclude that UBX proteins are transcriptional repressors and activators, and that their actions are mediated by binding to promoter region sequences. Each member of the UBX protein family has similar regulatory abilities, but the properties of synthetic mutant forms suggest that UBX proteins may have a modular design similar to other transcriptional regulators.
长期以来，人们一直认为果蝇的同源异型基因，如超双胸（Ubx）和触角足（Antp），在发育过程中通过控制各种靶基因的表达来选择体节身份。在此，我们描述了一种在培养的黑腹果蝇细胞中进行的共转染实验，该实验用于证明Ubx蛋白（UBX）能够抑制Antp启动子融合体并激活Ubx启动子融合体，这是遗传研究预测的活性。我们发现：（a）UBX蛋白调节了准确起始的Antp P1和Ubx转录本的水平；（b）Ubx启动子的激活需要下游的UBX结合位点簇；（c）结合位点序列足以赋予异源启动子调控能力，无论其方向或精确位置如何。我们得出结论，UBX蛋白是转录抑制因子和激活因子，其作用是通过与启动子区域序列结合来介导的。UBX蛋白家族的每个成员都具有相似的调控能力，但合成突变体形式的特性表明，UBX蛋白可能具有与其他转录调节因子相似的模块化设计。
