Nelson H B, Laughon A
Program of Cellular and Molecular Biology, University of Wisconsin-Madison 53706.
New Biol. 1990 Feb;2(2):171-8.
Segmentation in Drosophila melanogaster is controlled by a network of interacting genes, many of which encode a homeodomain that confers sequence-specific binding to DNA. One of these, fushi tarazu (ftz), is a transcription factor that regulates a number of segmentation and homeotic genes, including Antennapedia (Antp). To determine the DNA binding specificity of the ftz homeodomain, we performed DNase I footprint analysis on ftz protein binding sites located near the two Antp promoters using a beta-galactosidase/ftz fusion protein synthesized in E. coli. A consensus sequence for the fusion protein's preferred binding site was derived from 19 sites. The consensus sequence contains an ATTA motif, as do the reported consensus sequences for the engrailed (en), even-skipped (eve), and bicoid (bcd) Drosophila homeodomain proteins. We propose DNA bending as an explanation for the presence of a shared motif between proteins with divergent recognition helices: according to this model, bases in ATTA would not directly contact amino acid side chains of the recognition helix but rather would be necessary for bending of the DNA around the homeodomain, perhaps facilitating important protein-DNA contacts.
黑腹果蝇的体节形成由一个相互作用的基因网络控制，其中许多基因编码一个同源结构域，该结构域赋予与DNA的序列特异性结合能力。其中之一的ftz（分节基因）是一种转录因子，它调控许多体节形成和同源异型基因，包括触角足基因（Antp）。为了确定ftz同源结构域的DNA结合特异性，我们使用在大肠杆菌中合成的β-半乳糖苷酶/ftz融合蛋白，对位于两个Antp启动子附近的ftz蛋白结合位点进行了DNase I足迹分析。从19个位点推导出了融合蛋白偏好结合位点的共有序列。该共有序列包含一个ATTA基序，就像已报道的果蝇engrailed（en）、even-skipped（eve）和bicoid（bcd）同源结构域蛋白的共有序列一样。我们提出DNA弯曲来解释具有不同识别螺旋的蛋白质之间存在共享基序的现象：根据这个模型，ATTA中的碱基不会直接接触识别螺旋的氨基酸侧链，而是对于DNA围绕同源结构域的弯曲是必需的，这可能有助于重要的蛋白质-DNA接触。
