Serrano N, Brock H W, Maschat F
Département de Biologie du Développement, Institut Jacques Monod, CNRS et Université Paris 7, France.
Development. 1997 Jul;124(13):2527-36. doi: 10.1242/dev.124.13.2527.
In Drosophila, Engrailed is a nuclear regulatory protein with essential roles during embryonic development. Although Engrailed is a transcription factor, little progress has been achieved in identifying its target genes. We report here the identification of an effector gene, the beta3-tubulin gene, as a direct target of Engrailed. The cytological location of beta3-tubulin, 60C, is a strong site of Engrailed binding on polytene chromosomes. Immunostaining analysis of a transgenic line containing a P[beta3-tubulin-lacZ] construct shows an additional site of Engrailed binding at the location of the transgene. Molecular analysis allowed identification of several Engrailed binding sites, both in vitro and in vivo, within the first intron of the beta3-tubulin locus. Engrailed binding sites identified in vitro are active in larvae. Furthermore, expression of beta3-tubulin is derepressed in the ectoderm of engrailed mutant embryos. Repression of beta3-tubulin by Engrailed is also obtained when Engrailed is ectopically expressed in embryonic mesoderm. Finally, two different sets of Engrailed binding sites are shown to be involved in the early and late regulation of beta3-tubulin by Engrailed during embryogenesis.
在果蝇中，Engrailed是一种核调节蛋白，在胚胎发育过程中发挥着重要作用。尽管Engrailed是一种转录因子，但在鉴定其靶基因方面进展甚微。我们在此报告鉴定出一个效应基因，即β3-微管蛋白基因，它是Engrailed的直接靶标。β3-微管蛋白的细胞学定位60C是多线染色体上Engrailed结合的一个强位点。对含有P[β3-微管蛋白-乳糖操纵子]构建体的转基因品系进行免疫染色分析，结果显示在转基因位置存在Engrailed结合的另一个位点。分子分析使得在体外和体内均鉴定出β3-微管蛋白基因座第一个内含子内的几个Engrailed结合位点。在体外鉴定出的Engrailed结合位点在幼虫中具有活性。此外，β3-微管蛋白的表达在Engrailed突变胚胎的外胚层中去抑制。当Engrailed在胚胎中胚层异位表达时，也能观察到Engrailed对β3-微管蛋白的抑制作用。最后，研究表明在胚胎发育过程中，两组不同的Engrailed结合位点参与了Engrailed对β3-微管蛋白的早期和晚期调控。
