Analysis of the Inverse Effect in Drosophila

本研究的长期目标是利用黑腹果蝇的白眼颜色基因座作为模型系统，以剂量敏感的方式了解影响结构基因表达的调控基因的性质和机制。这种调节作用被认为与多细胞真核生物中大多数类型的结构基因的发育表达有关。非整倍体，或整倍体基因组中单个染色体数目的变化，与某些表型后果有关，据认为剂量调节剂在这些综合征的分子基础中起着重要作用。先前的工作已经确定了几个对白色表达产生剂量敏感修饰作用的基因。克隆或其他鉴定这些基因的方法表明它们是各种类型的转录因子和染色质成分。剂量效应的主要类型是调控因子的拷贝数与靶位点的表达呈负相关关系。如果调节剂和靶标同时变化，则影响抵消，产生剂量补偿。在这项工作中，对20个对白色有效的分子调控基因的相互作用进行研究，将确定当几个调控基因一起变化时，哪种类型的调控基因在建立基因表达的总体水平上占主导地位，就像在大型非整倍体中发生的那样。这些信息将有助于理解调控基因回路、非整倍体综合征、剂量补偿机制以及调控基因在数量性状控制中的作用。第二个主要方向将是分析一个新发现的全球调控复合体，似乎存在于多细胞真核生物中。同源复合体在酵母中是一个全球性的负调控系统，但在果蝇中预测的蛋白序列和作用存在显著差异。提出的功能测试将开始研究这些基因如何对多细胞物种的基因表达产生影响。最后，在之前的资助期内发现了与男性X染色体上男性特异性致死（MSL）复合物相关的成核位点的证据。假设的成核位点将被分离出来，并将研究它与X结合的机制。这些实验将探讨MSL蛋白如何改变剂量敏感调节基因的作用。该项目将有助于理解反向剂量调节，并解决是否有相关的调控基因与染色体剂量相关的生物学效应，如补偿，数量性状，非整倍体综合征和位置效应变异之间的联系。基因组不仅仅是一系列个体基因的集合。它是一个控制细胞和有机体功能的单位，是那些个体基因以精确和模式编排的复杂相互作用的结果。这项工作将更深入地了解这些相互作用以及它们如何影响单个靶位点的调节。

Birchler9807802The long range goal of the proposed work is to understand the nature and mechanism of transacting regulatory genes that affect the expression of structural genes in a dosage sensitive manner, utilizing the white eye color locus of Drosophila melanogaster as a model system. It is believed that this type of regulatory effect is involved in the developmental expression of most types of structural genes in multicellular eukaryotes. Aneuploidy, or the change of individual chromosome number in an otherwise euploid genome, is associated with certain phenotypic consequences and it is thought that the dosage regulators play a significant role in the molecular basis of these syndromes. Previous work has identified several genes that produce a dosage sensitive modifying effect on white expression. Cloning, or other means of identifying these genes, revealed them to be various types of transcriptional factors and chromatin components. The major type of dosage effect is an inverse correlation between the copy number of the regulator and the expression of the target locus. If the regulator and the target are varied together, the effects cancel to produce dosage compensation. In the proposed work, a study of the interactions of 20 molecularly defined regulatory genes that are effective on white will establish what types of regulatory genes predominate in establishing the overall level of gene expression when several regulators are varied together as would occur in large aneuploids. This information will be of value for understanding regulatory gene circuitry, aneuploid syndromes, dosage compensation mechanisms and involvement of regulatory genes in the control of quantitative traits. The second major direction will be to analyze a newly discovered global regulatory complex that appears to exist throughout multicellular eukaryotes. The orthologous complex acts in yeast as a global negative regulatory system, but there are significant differences in the predicted protein sequences and action in Drosophila. The functional tests proposed will begin work on how these genes produce their effect on gene expression in multicellular species. Lastly, evidence was found in the previous funding period for nucleation sites for the association of the male specific lethal (MSL) complex on the male X chromosome. The hypothesized nucleation site will be isolated and the mechanism by which it conditions binding to the X will be studied. These experiments will address how the MSL proteins act to modify the action of the dosage sensitive regulatory genes. The proposed project will contribute to an understanding of inverse dosage regulation and address whether there is a connection between the responsible regulatory genes and the biological effects associated with chromosomal dosage such as compensation, quantitative traits, aneuploid syndromes and position effect variegation.A genome is more than a series of individual genes. It is a unit whose control of cell and organismal function is the result of complex interactions of those individual genes in a precise and patterned choreography. This work will give greater insight into some of those interactions and how they affect the regulation of individual target loci.