CHROMATIN MACHINE--BRM AND SNR 1 PROTEINS IN A SWI/SNF-LIKE COMPLEX

许多酵母基因的转录激活依赖于 序列特异性DNA结合蛋白和最近发现的一种大分子 蛋白质复合体称为SWI/SNF复合体。酵母复合体被认为是 为了抵消染色质的抑制作用，可能是通过促进 DNA结合蛋白与其靶标的结合。的关键组件 SWI/SNF复合体是SW12/SNF2，一个可能是解旋酶的ATPase，以及SNF5， 这是一种新的蛋白质。我们已经鉴定了SNF5的果蝇同源物 (SNR1)和SW12(BRM)，并证明了它们之间的关联 产品在2×10/6道尔顿复合体中，与酵母大小大致相同 很复杂。果蝇的基因都是激活同源异型所必需的 (HOX)基因转录，使他们成为三胸(TRX)组的成员 激活剂。他们反对维持镇压的行动 功能，如聚梳(Pc)基因组。一种哺乳动物 SW12/SNF2同源基因已被报道与视网膜母细胞瘤有关 BRM的哺乳动物同源物蛋白质抑制肿瘤细胞的生长 培养，SNF5的同源物已被报道与HIV有关 整合酶。三胸杆菌本身编码的一种蛋白质与 Hrx，人类白血病原癌基因。我们建议使用的力量 果蝇发育遗传学以了解snrl和snrl的正常作用 BRM，这将阐明它们与肿瘤发生的联系。一个完整的基因 以及SNr1的发育特征，以了解SNr1在哪里和 在发育过程中需要基因的时候。准确的亚核位置 我们将对这些蛋白质进行研究。为了了解这两种蛋白质是如何 与BRM/Snr1复合体的其他成分以及蛋白质相互作用 那些不稳定的复合体成分，我们会用酵母两种 以SNr1或BRM为“诱饵”的杂交筛选。要探索 BRM/Snr1复合体转录激活的分子机制 会将这两个已知的成分蛋白与特定的靶基因连接在一起 活体测试激活情况，看看还需要哪些其他基因 这种激活。BRM/Snr1对特异性靶基因调控的研究 复合体，我们将测试现有的同源异型和其他 BRM和SNr1突变的潜在靶基因增强子。把这些放在一起 实验将极大地阐明分子和发育功能 新发现的建筑群。

The transcriptional activation of many yeast genes depends both on sequence-specific DNA binding proteins and on a recently identified large protein complex called the SWI/SNF complex. The yeast complex is thought to offset the repressive effects of chromatin, perhaps by facilitating the binding of DNA-binding proteins to their targets. Key components of the SWI/SNF complex are SW12/SNF2, an ATPase that may be a helicase, and SNF5, which is a novel protein. We have identified Drosophila homologs of SNF5 (snr1) and SW12 (brm) and have demonstrated the association of their products in a 2 x 10/6 dalton complex, about the same size as the yeast complex. The Drosophila genes are both required to activate homeotic (Hox) gene transcription, making them members of the trithorax (trx) group of activators. They oppose the actions of repression maintenance functions such as the Polycomb (Pc) group of genes. One mammalian SW12/SNF2 homolog has been reported to associate with Retinoblastoma protein, a mammalian homolog of brm inhibits growth of tumor cells in culture, and a SNF5 homolog has been reported to associate with HIV integrase. Trithorax itself encodes a protein with dramatic homology to HRX, a human leukemia proto-oncogene. We propose to use the power of Drosophila developmental genetics to learn the normal roles of snrl and brm which will shed light on their links to oncogenesis. A full genetic and developmental characterization of snr1 will be done to learn where and when the gene is required during development. Exact subnuclear locations of the proteins will be explored. To learn how these two proteins interact with other components of the brm/snr1 complex, and with proteins that are not stable components of the complex, we will use yeast two hybrid screening with either snr1 or brm as "bait". To explore the molecular mechanism of brm/snr1 complex transcriptional activation, we will tether the two known component proteins to specific target genes in vivo to test for activation and see which other genes are required for that activation. To study specific target gene regulation by brm/snr1 complex, we will test the response of existing homeotic and other potential target gene enhancers to brm and snr1 mutations. Together these experiments will greatly clarify the molecular and developmental functions of the newly discovered complex.