Lebrecht Danielle, Foehr Marisa, Smith Eric, Lopes Francisco J P, Vanario-Alonso Carlos E, Reinitz John, Burz David S, Hanes Steven D
Wadsworth Center, New York State Department of Health, 120 New Scotland Avenue, Albany, NY 12208, USA.
Proc Natl Acad Sci U S A. 2005 Sep 13;102(37):13176-81. doi: 10.1073/pnas.0506462102. Epub 2005 Sep 6.
Cooperative interactions by DNA-binding proteins have been implicated in cell-fate decisions in a variety of organisms. To date, however, there are few examples in which the importance of such interactions has been explicitly tested in vivo. Here, we tested the importance of cooperative DNA binding by the Bicoid protein in establishing a pattern along the anterior-posterior axis of the early Drosophila embryo. We found that bicoid mutants specifically defective in cooperative DNA binding fail to direct proper development of the head and thorax, leading to embryonic lethality. The mutants did not faithfully stimulate transcription of downstream target genes such as hunchback (hb), giant, and Krüppel. Quantitative analysis of gene expression in vivo indicated that bcd cooperativity mutants were unable to accurately direct the extent to which hb is expressed along the anterior-posterior axis and displayed a reduced ability to generate sharp on/off transitions for hb gene expression. These failures in precise transcriptional control demonstrate the importance of cooperative DNA binding for embryonic patterning in vivo.
DNA结合蛋白的协同相互作用已被证明与多种生物体的细胞命运决定有关。然而，迄今为止，很少有例子能在体内明确测试这种相互作用的重要性。在这里，我们测试了双胸蛋白协同结合DNA在果蝇早期胚胎前后轴上建立模式中的重要性。我们发现，在协同DNA结合方面存在特异性缺陷的双胸突变体无法指导头部和胸部的正常发育，导致胚胎致死。这些突变体不能如实地刺激下游靶基因如驼背（hb）、巨人基因和克鲁佩尔基因的转录。体内基因表达的定量分析表明，双胸协同性突变体无法准确指导hb基因沿前后轴的表达程度，并且在产生hb基因表达的尖锐开/关转换方面能力降低。这些精确转录控制的失败证明了协同DNA结合在体内胚胎模式形成中的重要性。
