Kelly Kathleen K, Meadows Stryder M, Cripps Richard M
Department of Biology, University of New Mexico, Albuquerque, NM 87131-1091, USA.
Mech Dev. 2002 Jan;110(1-2):39-50. doi: 10.1016/s0925-4773(01)00586-x.
To identify regulatory events occurring during myogenesis, we characterized the transcriptional regulation of a Drosophila melanogaster actin gene, Actin 57B. Act57B transcription is first detected in visceral muscle precursors and is detectable in all embryonic muscles by the end of embryogenesis. Through deletion analysis we identified a 595 bp promoter element that was sufficient for high levels of expression in all three muscle lineages. This fragment contained a MEF2 binding site conserved between D. melanogaster and Drosophila virilis which bound MEF2 protein in embryo nuclear extracts. Mutation of the MEF2 site severely reduced promoter activity in embryos, and in Mef2 mutants Act57B expression was severely decreased, demonstrating MEF2 is an essential regulator of Act57B. We also showed that MEF2 likely acts synergistically with factors bound to additional sequences within the 595 bp element. These findings underline the importance of MEF2 in controlling differentiation in all muscle lineages. Our experiments reveal a novel regulatory mechanism for a structural gene where high levels of expression in all embryonic muscles is regulated through a single transcription factor binding site.
为了识别在肌生成过程中发生的调控事件，我们对果蝇肌动蛋白基因Actin 57B的转录调控进行了表征。Act57B转录首先在内脏肌前体中被检测到，并且在胚胎发育结束时在所有胚胎肌肉中都可检测到。通过缺失分析，我们鉴定出一个595 bp的启动子元件，该元件足以在所有三个肌肉谱系中实现高水平表达。该片段包含一个在黑腹果蝇和拟果蝇之间保守的MEF2结合位点，该位点在胚胎核提取物中与MEF2蛋白结合。MEF2位点的突变严重降低了胚胎中的启动子活性，并且在Mef2突变体中，Act57B表达严重下降，表明MEF2是Act57B的必需调节因子。我们还表明，MEF2可能与结合在595 bp元件内其他序列上的因子协同作用。这些发现强调了MEF2在控制所有肌肉谱系分化中的重要性。我们的实验揭示了一种结构基因的新型调控机制，即通过单个转录因子结合位点调控所有胚胎肌肉中的高水平表达。
