Chemical Probes Targeting Polycomb Repressive Complex 2 Gene Repression

描述(申请人提供)：聚梳组蛋白(PcG)是转录抑制因子，它结合编码蛋白质的基因的启动子，在许多细胞谱系中起着决定细胞命运的关键作用。这些蛋白质通过沉默不适当的表达和维持染色质抑制状态来调节它们的功能。已知PCG蛋白形成两种常见类型的大的多聚体复合体，即PRC1和PRC2。PrC2参与了基因抑制的启动，它具有内源性的组蛋白甲基转移酶活性，对组蛋白H3(H3K27)的27位赖氨酸具有专一性，而PrC1在转录抑制中起重要作用。大量文献将PRC2组分EZH2、EED和SUZ12与肿瘤发生、不良预后和肿瘤增殖联系起来。这些蛋白的过度表达会导致该复合体的酶活性升高，从而在多种癌症中转化为肿瘤抑制基因的异常抑制。因此，用化学探针靶向灭活PRC2复合体已成为开发新的表观遗传癌症治疗方法的高度优先策略。这一观点得到了先前研究的支持，在这些研究中，EZH2或EED的敲除或敲除会损害MLL-AF9细胞的增殖，最近的报告显示，禁用PRC2复合体活性对治疗PCR2依赖的人类癌症是有效的。尽管PcG蛋白在癌症生物学中很重要，但PcG成员个体的功能仍然知之甚少。我们现在才刚刚开始了解PcG蛋白实际上是如何调节它们的目标基因的。因此，发现新的研究工具有助于阐明这些基本的表观遗传调节因子在肿瘤发展中的具体作用是一个非常有兴趣的领域。这项建议试图通过首次开发有效的、蛋白质分解稳定的PcG蛋白EED和SUZ12的模拟肽和小分子抑制剂来满足这一需求，PcG蛋白是PRC2复合体的两个关键成分。我们假设，选择性地抑制EED或SUZ12/抑制性三甲基赖氨酸结合将取消PRC2的催化活性，从而取消其生物学功能。因此，这些化学配体不仅可以用于研究该蛋白在不同细胞过程中的特殊作用，还可以用于破译PR2靶基因在癌症生物学中的作用。

DESCRIPTION (provided by applicant): Polycomb group proteins (PcG) are transcriptional repressors that bind the promoters of genes encoding proteins with key roles in cell fate determination in many cellular lineages. These proteins mediate their functions by silencing inappropriate expressions and maintaining a chromatin repressive state. PcG proteins are known to form large multimeric complexes of two general types, PRC1 and PRC2. PRC2 is involved in the initiation of gene repression and it has intrinsic histone methyltransferase activiy, with specificity for lysine 27 of histone H3 (H3K27), whereas PRC1 is important for effecting transcriptional repression. A large body of literature links PRC2 components EZH2, EED and SUZ12 to tumor genesis, poor prognosis and tumor proliferation. Overexpression of these proteins leads to enzymatic hyperactivity of the complex, which translates into aberrant repression of tumor suppressor genes in diverse cancers. Thus, targeting the inactivation of the PRC2 complex with chemical probes has emerged as a high-priority strategy to develop novel epigenetic cancer therapies. This idea has been supported by prior studies in which knockdown or knockout of EZH2 or EED impaired proliferation of MLL-AF9 cells, and by recent reports showing the utility of disabling PRC2 complex activity for the treatment of PCR2-dependent human cancers. Despite the importance of PcG proteins in cancer biology, the function of individual PcG members is still poorly understood. We are only beginning to understand now how the PcG proteins actually regulate their target genes. Discovering novel research tools useful to elucidate the specific role of these basic epigenetic regulators in neoplastic development is, therefore, an area of great interest. This proposal attempts to address this need by developing, for the first time, potent and proteolytically stable peptidomimetic and small-molecule inhibitors of the PcG proteins EED and SUZ12, two key components of the PRC2 complex. We have hypothesized that selective inhibition of the EED or SUZ12/repressive trimethyl-lysine association will abolish the PRC2 catalytic activity, and consequently, its biological functions. Hence, these chemical ligands could be useful not only to study the particular role of this protein in different cellular processes but also to decipher the role of PR2 target genes in cancer biology.