de Celis J F, de Celis J, Ligoxygakis P, Preiss A, Delidakis C, Bray S
Department of Genetics, University of Cambridge, UK.
Development. 1996 Sep;122(9):2719-28. doi: 10.1242/dev.122.9.2719.
The basic helix-loop-helix proteins of the Enhancer of split complex constitute a link between activation of the transmembrane receptor Notch and the resulting effects on transcription of downstream genes. The Suppressor of Hairless protein is the intermediary between Notch activation and expression of all Enhancer of split genes even though individual genes have distinct patterns of expression in imaginal discs. A comparison between the phenotypes produced by Notch, Suppressor of Hairless and Enhancer of split mutations in the wing and thorax indicate that Suppressor of Hairless and Notch requirements are indistinguishable, but that Enhancer of split activity is only essential for a subset of developmental processes involving Notch function. Likewise, the ectopic expression of Enhancer of split proteins does not reproduce all the consequences typical of ectopic Notch activation. We suggest that the Notch pathway bifurcates after the activation of Suppressor of Hairless and that Enhancer of split activity is not required when the consequence of Notch function is the transcriptional activation of downstream genes. Transcriptional activation mediated by Suppressor of Hairless and transcriptional repression mediated by Enhancer of split could provide greater diversity in the response of individual genes to Notch activity.
分裂复合物增强子的基本螺旋-环-螺旋蛋白构成了跨膜受体Notch激活与下游基因转录所产生效应之间的联系。无毛抑制蛋白是Notch激活与所有分裂增强子基因表达之间的中介，尽管各个基因在成虫盘中有不同的表达模式。对翅膀和胸部中Notch、无毛抑制蛋白和分裂增强子突变所产生的表型进行比较表明，无毛抑制蛋白和Notch的需求难以区分，但分裂增强子活性仅对涉及Notch功能的一部分发育过程至关重要。同样，分裂增强子蛋白的异位表达并不会重现异位Notch激活的所有典型后果。我们认为，在无毛抑制蛋白激活后Notch信号通路发生分支，并且当Notch功能的结果是下游基因的转录激活时，不需要分裂增强子活性。由无毛抑制蛋白介导的转录激活和由分裂增强子介导的转录抑制可以为单个基因对Notch活性的反应提供更大的多样性。
