Pan D J, Huang J D, Courey A J
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024-1569.
Genes Dev. 1991 Oct;5(10):1892-901. doi: 10.1101/gad.5.10.1892.
twist is one of the earliest expressed zygotically active genes required for dorsal-ventral pattern formation in the Drosophila embryo. Genetic studies suggest that this gene is activated in the ventral part of the blastoderm by maternally expressed dorsal gene product. Using P-element-mediated germ-line transformation, we have mapped a small (260 bp) dorsal-dependent ventral activator region (VAR) in the 5'-flanking region of the twist promoter that can direct the early ventral expression of a heterologous promoter. The VAR contains binding sites for a number of proteins present in extracts of Drosophila embryos. One of these sites bears homology to known binding sites for the dorsal transcription factor and is specifically bound by bacterially expressed dorsal protein. Furthermore, a 37-bp deletion that removes the dorsal-binding sequences abolishes the ventral-specific activity of the twist promoter constructs. Our data also show that additional sequences within the VAR are required to render the dorsal-binding sites functional. Finally, reverse genetic and biochemical data suggest that the transcription factor, encoded by the zeste gene may help control the overall level, if not the pattern, of twist expression.
“twist”是果蝇胚胎背腹模式形成所需的最早表达的合子活性基因之一。遗传学研究表明，该基因在胚盘的腹侧部分由母体表达的“dorsal”基因产物激活。利用P因子介导的种系转化，我们在“twist”启动子的5'侧翼区域定位了一个小的（260 bp）依赖于“dorsal”的腹侧激活区域（VAR），它可以指导异源启动子的早期腹侧表达。VAR包含果蝇胚胎提取物中存在的多种蛋白质的结合位点。其中一个位点与已知的背侧转录因子结合位点具有同源性，并被细菌表达的背侧蛋白特异性结合。此外，一个去除背侧结合序列的37 bp缺失消除了“twist”启动子构建体的腹侧特异性活性。我们的数据还表明，VAR内的其他序列是使背侧结合位点发挥功能所必需的。最后，反向遗传学和生化数据表明，由“zeste”基因编码的转录因子可能有助于控制“twist”表达的总体水平，如果不是表达模式的话。
