GENETIC AND MOLECULAR STUDIES OF THE BRM GENE

双胸和双足复合体的同源异型基因编码 空间限制性转录因子，指导选择 替代发展途径。同源异型基因的调控 因此，转录对果蝇中细胞命运的控制至关重要。 我们的长期目标是在分子水平上了解 建立同源异型基因转录的空间模式， 在果蝇的整个发育过程中都是如此。遗传学研究 确定了许多控制同源异型转录的基因， 基因在发展过程中，包括Polycomb，同源异型的阻遏物， 基因.尽管最近的研究表明Polycomb抑制了 同源异型基因转录通过影响染色质结构，其确切 作用机制未知。确定其他监管机构， 同源异型基因转录，我们已经筛选了显性抑制因子， 多梳突变。在这些筛选中鉴定出的基因之一brahma (brm)编码同源异型基因的激活因子， 酵母转录激活因子SNF2/SWI2。的蛋白质的基因 在小鼠中也发现了与BRM高度相关的基因， 人类在酵母中，SNF2/SWI2协助DNA结合调节蛋白， 克服染色质对转录的抑制作用。基于 BRM和SNF2/SWI2之间的相似性，我们提出BRM 通过协助DNA结合激活同源异型基因的转录 调节蛋白，以克服Polycomb对 染色质结构本提案中描述的实验是 旨在批判性地检验这一假设，并澄清分子 BRM的作用机制我们将确定brm的作用， 胚胎、幼虫和蛹阶段的果蝇发育， 系和体细胞克隆分析。来确定BRM是否是一个函数 SNF2/SWI2的同源物，我们将测试brm蛋白的能力， 在酵母中的体内功能。将进行生化研究， 识别和表征brm相关蛋白，以及相互作用 用多线染色体检测BRM与其靶基因之间的关系 免疫染色。我们还将研究brm蛋白在 使用相对简单的体外系统进行转录激活。

The homeotic genes of the Antennapedia and bithorax complexes encode spatially-restricted transcription factors that direct the choice between alternative pathways of development. The regulation of homeotic gene transcription is thus critical to the control of cell fate in Drosophila. Our long-term goal is to understand, at the molecular level, how the spatial patterns of homeotic gene transcription are established and maintained throughout Drosophila development. Genetic studies have identified many of the genes that control the transcription of homeotic genes during development, including Polycomb, a repressor of homeotic genes. Although recent studies have suggested that Polycomb represses homeotic gene transcription by influencing chromatin structure, its exact mechanism of action is unknown. To identify additional regulators of homeotic gene transcription, we have screened for dominant suppressors of Polycomb mutations. One of the genes identified in these screens, brahma (brm), encodes an activator of homeotic genes that is structurally related to the yeast transcriptional activator SNF2/SWI2. Genes encoding proteins that are highly related to brm have also been identified in mice and humans. In yeast, SNF2/SWI2 assists DNA-binding regulatory proteins to overcome the repressive effects of chromatin on transcription. Based on the similarities between brm and SNF2/SWI2, we have proposed that brm activates the transcription of homeotic genes by assisting DNA-binding regulatory proteins to overcome the repressive effects of Polycomb on chromatin structure. The experiments described in this proposal are designed to critically examine this hypothesis, and clarify the molecular mechanism of brm action. We will determine the role of brm during embryonic, larval and pupal stages of Drosophila development using germ- line and somatic clonal analysis. To determine whether brm is a functional homolog of SNF2/SWI2, we will test the ability of the brm protein to function in vivo in yeast. Biochemical studies will be conducted to identify and characterize brm-associated proteins, and the interactions between brm and its target genes will be examined by polytene chromosome immunostaining. We will also study the role of the brm protein in transcriptional activation using a relatively simple in vitro system.