Dawson S R, Turner D L, Weintraub H, Parkhurst S M
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
Mol Cell Biol. 1995 Dec;15(12):6923-31. doi: 10.1128/MCB.15.12.6923.
The Hairy/Enhancer of split/Deadpan family of basic helix-loop-helix (bHLH) proteins function as transcriptional repressors. We have examined the mechanisms of repression used by the Hairy and E(SPL) proteins by assaying the antagonism between wild-type or altered Hairy/E(SPL) and Scute bHLH proteins during sex determination in Drosophila melanogaster. Domain swapping and mutagenesis of the Hairy and E(SPL) proteins show that three evolutionarily conserved domains are required for their function: the bHLH, Orange, and WRPW domains. However, the suppression of Scute activity by Hairy does not require the WRPW domain. We show that the Orange domain is an important functional domain that confers specificity among members of the Hairy/E(SPL) family. In addition, we show that a Xenopus Hairy homology conserves not only Hairy's structure but also its biological activity in our assays. We propose that transcriptional repression by the Hairy/E(SPL) family of bHLH proteins involves two separable mechanisms: repression of specific transcriptional activators, such as Scute, through the bHLH and Orange domains and repression of other activators via interaction of the C-terminal WRPW motif with corepressors, such as the Groucho protein.
碱性螺旋-环-螺旋（bHLH）蛋白家族中的毛状/分裂增强子/冷面蛋白作为转录抑制因子发挥作用。我们通过检测野生型或改变后的毛状/E（SPL）与Scute bHLH蛋白在黑腹果蝇性别决定过程中的拮抗作用，研究了毛状蛋白和E（SPL）蛋白所使用的抑制机制。毛状蛋白和E（SPL）蛋白的结构域交换和诱变表明，其功能需要三个进化上保守的结构域：bHLH、橙色和WRPW结构域。然而，毛状蛋白对Scute活性的抑制并不需要WRPW结构域。我们表明橙色结构域是一个重要的功能结构域，赋予毛状/E（SPL）家族成员特异性。此外，我们表明非洲爪蟾的毛状蛋白同源物不仅保留了毛状蛋白的结构，而且在我们的实验中保留了其生物学活性。我们提出，bHLH蛋白家族的毛状/E（SPL）蛋白的转录抑制涉及两种可分离的机制：通过bHLH和橙色结构域抑制特定的转录激活因子，如Scute，以及通过C末端WRPW基序与共抑制因子（如Groucho蛋白）的相互作用抑制其他激活因子。
