Tietze K, Oellers N, Knust E
Institut für Entwicklungsbiologie, Universität zu Köln, Federal Republic of Germany.
Proc Natl Acad Sci U S A. 1992 Jul 1;89(13):6152-6. doi: 10.1073/pnas.89.13.6152.
Helix-loop-helix proteins play important roles in developmental processes, such as myogenesis, neurogenesis, and sex determination. The gene Enhancer of split [E(spl)] of Drosophila, a member of a gene complex that is involved in early neurogenesis, encodes a protein with a basic domain and a helix-loop-helix motif. We took advantage of a dominant mutation of this gene, E(spl)D, to define in vivo structural features of this protein for proper function. The mutation renders the otherwise recessive eye phenotype of spl dominant. By germ-line transformation of different in vitro mutagenized versions of the E(spl) gene, we could demonstrate that the basic domain of this helix-loop-helix protein is functional and necessary for expression of the dominant phenotype. These results are supported by in vitro DNA-binding assays, which showed that the basic domain is in fact necessary for DNA binding, despite the presence of a proline residue. Furthermore, we could show that the dominant enhancement of spl is caused by truncation of the E(SPL)D protein in combination with deletion of a putative regulatory element.
螺旋-环-螺旋蛋白在发育过程中发挥重要作用，如在肌生成、神经发生和性别决定等过程中。果蝇的分裂增强子基因[E(spl)]是一个参与早期神经发生的基因复合体的成员，它编码一种具有碱性结构域和螺旋-环-螺旋基序的蛋白质。我们利用该基因的显性突变E(spl)D来确定该蛋白质在体内发挥正常功能所需的结构特征。该突变使原本隐性的spl眼表型变为显性。通过对不同体外诱变版本的E(spl)基因进行种系转化，我们能够证明这种螺旋-环-螺旋蛋白的碱性结构域对于显性表型的表达是有功能且必需的。体外DNA结合试验支持了这些结果，试验表明尽管存在一个脯氨酸残基，但碱性结构域实际上对于DNA结合是必需的。此外，我们能够表明spl的显性增强是由E(SPL)D蛋白的截短与一个假定调控元件的缺失共同导致的。
