Singson A, Leviten M W, Bang A G, Hua X H, Posakony J W
Department of Biology, University of California San Diego, La Jolla 92093-0322.
Genes Dev. 1994 Sep 1;8(17):2058-71. doi: 10.1101/gad.8.17.2058.
In Drosophila imaginal discs, the spatially restricted activities of the achaete (ac) and scute (sc) proteins, which are transcriptional activators of the basic-helix-loop-helix class, define proneural clusters (PNCs) of potential sensory organ precursor (SOP) cells. Here, we report the identification of several genes that are direct downstream targets of ac-sc activation, as judged by the following criteria. The genes are expressed in the PNCs of the wing imaginal disc in an ac-sc-dependent manner; the proximal promoter regions of all of these genes contain one or two high-affinity ac-sc binding sites, which define the novel consensus GCAGGTG(T/G)NNNYY; where tested, these binding sites are required in vivo for PNC expression of promoter-reporter fusion genes. Interestingly, these ac-sc target genes, including Bearded, Enhancer of split m7, Enhancer of split m8, and scabrous, are all known or believed to function in the selection of a single SOP from each PNC, a process mediated by inhibitory cell-cell interactions. Thus, one of the earliest steps in adult peripheral neurogenesis is the direct activation by proneural proteins of genes involved in restricting the expression of the SOP cell fate.
在果蝇成虫盘里，无刚毛（ac）和粗糙（sc）蛋白具有空间限制活性，它们是碱性螺旋-环-螺旋类的转录激活因子，可界定潜在感觉器官前体细胞（SOP）的原神经细胞簇（PNC）。在此，我们报告鉴定出了几个基因，根据以下标准判断，它们是ac-sc激活的直接下游靶点。这些基因以ac-sc依赖的方式在翅成虫盘的PNC中表达；所有这些基因的近端启动子区域都包含一个或两个高亲和力的ac-sc结合位点，其界定了新的共有序列GCAGGTG(T/G)NNNYY；在经过测试的情况下，这些结合位点在体内对于启动子-报告基因融合基因的PNC表达是必需的。有趣的是，这些ac-sc靶基因，包括芒状蛋白、分裂增强子m7、分裂增强子m8和粗糙蛋白，都已知或被认为在从每个PNC中选择单个SOP的过程中发挥作用，这一过程由抑制性细胞间相互作用介导。因此，成虫外周神经发生的最早步骤之一是原神经蛋白直接激活参与限制SOP细胞命运表达的基因。
