Braun T, Winter B, Bober E, Arnold H H
Department of Toxicology, Medical School, University of Hamburg, FRG.
Nature. 1990 Aug 16;346(6285):663-5. doi: 10.1038/346663a0.
The human muscle determination factor myf5, like MyoD and other members of the family of skeletal muscle-specific regulatory proteins, contains a highly conserved putative helix-loop-helix domain. In MyoD this motif is required for the initiation of myogenesis in C3H mouse 10T1/2 fibroblasts and other non-muscle cells as well as for transcriptional activation of muscle genes. High affinity DNA binding of MyoD to regulatory DNA elements in muscle genes requires the formation of heterodimers with ubiquitous helix-loop-helix proteins such as E12 or E47. To investigate the potential of myf5 as a transcription factor, we have fused the GAL4 DNA-binding domain to various parts of the myf5 protein and analysed the transactivation of a GAL4 reporter plasmid. Here we report that myf5 contains an intrinsic transcriptional activation domain which is distinct from the helix-loop-helix motif. The predominant transactivating effect is associated with the C-terminal half of the myf5 molecule. High-affinity sequence-specific DNA binding of myf5 also requires hetero-oligomeric association with the enhancer-binding protein E12 to confer muscle-specific transactivation.
人类肌肉决定因子myf5，与MyoD以及骨骼肌特异性调节蛋白家族的其他成员一样，含有一个高度保守的假定螺旋-环-螺旋结构域。在MyoD中，这个基序对于C3H小鼠10T1/2成纤维细胞和其他非肌肉细胞中肌生成的起始以及肌肉基因的转录激活是必需的。MyoD与肌肉基因中的调节DNA元件的高亲和力DNA结合需要与普遍存在的螺旋-环-螺旋蛋白如E12或E47形成异二聚体。为了研究myf5作为转录因子的潜力，我们将GAL4 DNA结合结构域与myf5蛋白的不同部分融合，并分析了GAL4报告质粒的反式激活。在此我们报告，myf5含有一个与螺旋-环-螺旋基序不同的内在转录激活结构域。主要的反式激活作用与myf5分子的C端一半相关。myf5的高亲和力序列特异性DNA结合也需要与增强子结合蛋白E12进行异源寡聚体结合，以赋予肌肉特异性反式激活作用。
