Genome Wide Measurement of Concentration Dependent Bicoid Transcription Factor Binding

描述(申请人提供)：为了使胚胎发育正确和可重复地进行，胚胎单个细胞中的基因表达必须精确地协调。实现基因表达的时空协调的一种方式是通过转录因子的作用，转录因子是与DNA结合并调节特定靶基因表达的蛋白质。在果蝇胚胎中，母体提供的转录因子BCD(BCD)为形成胚胎的前后轴(AP)提供了位置信息。BCD蛋白从胚胎的前极扩散，已知与基因组中超过1000个位置结合，从而激活沿AP轴不同位置的至少20个靶基因。传统的模型认为胚胎中的位置信息是BCD浓度的直接读数。虽然最近的研究对这一模型提出了挑战，但局部BCD浓度、DNA结合和靶基因表达之间的机制关系尚不清楚。本文提出的实验旨在直接测量体内BCD DNA结合和靶基因表达的浓度依赖性。这项工作将阐明蛋白质浓度对转录因子控制其靶标表达的能力的影响。

DESCRIPTION (provided by applicant): In order for embryonic development to proceed correctly and reproducibly, the expression of genes in individual cells of an embryo must be coordinated with precision. One way in which temporal and spatial coordination of gene expression is achieved is through the action of transcription factors, proteins which bind to DNA and regulate expression of specific target genes. In Drosophila embryos, the maternally provided transcription factor Bicoid (Bcd) provides the positional information to pattern the anterior-posterior (AP) axis of the embryo. Bcd protein diffuses from the anterior pole of the embryo and is known to bind to over 1000 sites in the genome, thereby activating at least twenty target genes at different positions along the AP axis. A traditional model suggests the positional information in an embryo is a direct readout of Bcd concentration. Although recent studies have challenged this model, the mechanistic relationship between local Bcd concentration, DNA binding, and target gene expression is unknown. The experiments proposed here aim to directly measure the in vivo concentration-dependence of Bcd DNA binding and target gene expression. This work will elucidate the effects of protein concentration on the ability of transcription factors to control the expression of their targets.