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大 蛋白质复合物称为SWI/SNF复合物。 酵母复合体被认为 以抵消染色质的抑制作用，也许是通过促进 DNA结合蛋白与其靶标的结合。 关键部件 SWI/SNF复合物是SW 12/SNF 2，一种可能是解旋酶的ATP酶，和SNF 5， 这是一种新的蛋白质。 我们已经鉴定出果蝇的SNF 5同源物， （snr 1）和SW 12（brm），并已证明其相关性， 产物为2 × 10/6道尔顿复合物，大小与酵母相同 复杂. 果蝇的基因都需要激活同源异型 (Hox)基因转录，使它们成为三胸（trx）组的成员 激活剂。 他们反对镇压维护的行动 例如Polycomb（Pc）基因组。 一种哺乳动物 SW 12/SNF 2同源物与视网膜母细胞瘤相关 一种与BRM同源的哺乳动物蛋白质， 据报道，SNF 5同源物与HIV有关 整合酶 三胸本身编码一种蛋白质， HRX，一种人类白血病原癌基因。 我们建议利用 果蝇的发育遗传学，以了解snrl和 BRM将揭示它们与肿瘤发生的联系。 完整的基因 和SNR 1的发育特征将被完成，以了解在哪里， 基因在发育过程中是必需的。 精确的亚核位置 蛋白质将被探索。 为了了解这两种蛋白质 与BRM/SNR 1复合物的其他组分以及蛋白质相互作用 不是复合物的稳定成分，我们将使用酵母二 用SNR 1或BRM作为“诱饵”进行杂交筛选。 探讨 BRM/SNR 1复合物转录激活的分子机制，我们 将这两种已知的蛋白质组分与特定的靶基因连接在一起， 体内测试激活，看看其他基因所需的 这种激活。 研究BRM/SNR 1对靶基因的特异性调控 复杂，我们将测试现有的同源异型和其他反应， BRM和SNR 1突变的潜在靶基因增强子。 综合这些 实验将极大地澄清分子和发育功能， 新发现的复合体。

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.