Huang J D, Schwyter D H, Shirokawa J M, Courey A J
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024-1569.
Genes Dev. 1993 Apr;7(4):694-704. doi: 10.1101/gad.7.4.694.
The product of the zygotically active decapentaplegic (dpp) gene appears to function as a morphogen that specifies positional information in the dorsal half of the Drosophila embryo. The dorsal-specific transcription of dpp is the key step in establishing a morphogen gradient. We demonstrate here that multiple regions within the second intron of the gene cooperate with one another to generate the wild-type level and pattern of dpp transcription. These regions contain both generalized enhancer elements as well as ventral-specific repressor elements. Placed within the context of heterologous promoters, the intron retains its ability to direct general activation and ventral repression. The ventral specific repression of dpp transcription is directly mediated by binding sites for the dorsal (dl) morphogen in the repressor elements. In contrast with the zerknüllt (zen) ventral repressor element, which contains a few high-affinity dl-binding sites, dpp contains multiple relatively low-affinity sites that function together to bring about complete ventral repression. Because dpp and zen have nearly coincident early expression domains, these results indicate that the same boundary of repression can be specified by dl-binding sites of different affinity. We discuss the possibility that unknown factors interact with dl protein to determine the domain of dl-mediated repression.
合子激活的果蝇“五体不全”基因（dpp）的产物似乎起着形态发生素的作用，它能确定果蝇胚胎背部一半区域的位置信息。dpp基因的背部特异性转录是建立形态发生素梯度的关键步骤。我们在此证明，该基因第二内含子内的多个区域相互协作，以产生野生型水平的dpp转录及其模式。这些区域既包含通用增强子元件，也包含腹部特异性抑制元件。置于异源启动子的背景下，该内含子仍保留其指导一般激活和腹部抑制的能力。dpp转录的腹部特异性抑制直接由抑制元件中背侧（dl）形态发生素的结合位点介导。与含有少数高亲和力dl结合位点的“零乱”（zen）腹部抑制元件不同，dpp含有多个相对低亲和力的位点，它们共同作用以实现完全的腹部抑制。由于dpp和zen具有几乎重合的早期表达结构域，这些结果表明，不同亲和力的dl结合位点可以确定相同的抑制边界。我们讨论了未知因子与dl蛋白相互作用以确定dl介导的抑制结构域的可能性。
