GENETIC AND MOLECULAR STUDIES OF THE BRM GENE

触角线虫和双胸复合体的同源异型基因编码 空间受限的转录因子，指导在 可选择的发展道路。同源异型基因的调控 因此，转录对于控制果蝇的细胞命运至关重要。 我们的长期目标是在分子水平上了解 建立了同源异型基因转录的空间模式，并 在果蝇的整个发育过程中保持不变。基因研究已经 鉴定了许多控制同源异型基因转录的基因 发育过程中的基因，包括同源异型的抑制因子Polycomb 基因。尽管最近的研究表明，Polycomb抑制了 同源异型基因转录对染色质结构的影响 其作用机制尚不清楚。确定更多的监管机构 同源异型基因转录，我们已经筛选出显性抑制因子 多梳突变。在这些筛查中发现的基因之一，梵天 (BRM)，编码一种结构上相关的同源异型基因的激活因子 酵母转录激活子SNF2/SWI2。编码蛋白质的基因 与BRM高度相关的基因也在小鼠和 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 由于BRM与SNF2/SWI2的相似性，我们提出了BRM 通过协助DNA结合来激活同源异型基因的转录 克服Polycomb抑制作用的调节蛋白 染色质结构。本提案中描述的实验包括 旨在批判性地检验这一假说，并澄清分子 BRM的作用机制。我们将确定BRM在 果蝇胚胎期、幼虫期和幼虫期的发育 品系和体细胞克隆分析。要确定BRM是否正常工作 SNF2/SWI2的同源物，我们将测试BRM蛋白对 在酵母中的体内功能。我们会进行生化研究，以 鉴定和鉴定BRM相关蛋白及其相互作用 BRM与其靶基因之间的关系将通过多线染色体进行检测 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.