Investigating essential chromatin regulators in cancers with SWI/SNF mutations

项目总结 在近25%的癌症中，编码SWI/SNF染色质重塑复合体亚单位的基因发生了突变。 此外，SWI/SNF亚基的胚系突变会导致几种神经发育障碍。然而， 人们对这些突变导致癌症和疾病的机制知之甚少。SWI/SNF 复合体在增强子和启动子上动员核小体来调节转录。双等位基因失活 SMARCB1是一种编码SWI/SNF复合体亚单位的基因，可引起儿童横纹肌样肿瘤(RTS)。这些高度 侵袭性软组织肿瘤发生在婴幼儿，预后极差。自RT以来 基因组是二倍体，缺乏其他突变，是研究SWI/SNF特异性驱动机制的理想选择 用于治疗癌症和确定新的治疗靶点。我的导师和他的合作者发起了儿科 癌症依赖项目，以确定儿童癌症的新驱动因素和治疗靶点，包括RT。 对10个RT细胞系和800多个其他癌细胞系进行全基因组CRISPR筛查 揭示了SMARCB1缺陷RT特异依赖的一种新基因。这项提议旨在 为了研究这个假定的染色质调节因子的功能并确定它为什么构成一个 RT中的特定依赖项。该基因的过度表达与几种癌症的预后不良有关 因此，开发化学抑制剂的药理学努力已经在进行中。有趣的是，初步的 实验表明，这种蛋白可能控制组蛋白翻译后修饰(PTM)，从而决定 SWI/SNF复合体的重塑和基因表达。理解RT细胞依赖该蛋白质的原因 将揭示染色质调节的新机制，并可能确定新的治疗靶点 这些致命的癌症。我的中心假设是，这种蛋白控制组蛋白PTMS，是 唯一缺乏SMARCB1的SWI/SNF复合体家族的染色质招募，从而使它 在RT中必不可少。这项提案将调查缺乏酶活性的监管机构如何控制这些 组蛋白PTMS以及这如何影响染色质的可及性。此外，它将决定这个监管机构如何 影响SWI/SNF复合体调控的重塑和基因表达。总体而言，这项提议将 揭示这种相对研究较少的蛋白质的功能，为染色质的功能提供新的见解 受调控，解释为什么RTS选择性地依赖这种蛋白质生存，并可能识别一种新的 儿童致死性横纹肌样瘤的治疗靶点。此外，这项提案旨在解决我的 培训目标是在实验和计算方面熟练研究染色质生物学。

PROJECT SUMMARY Genes that encode subunits of SWI/SNF chromatin remodeling complexes are mutated in nearly 25% of cancers. Additionally, germline mutations in SWI/SNF subunits cause several neurodevelopmental disorders. However, the mechanisms by which these mutations drive cancer and disease are poorly understood. SWI/SNF complexes mobilize nucleosomes at enhancers and promoters to modulate transcription. Biallelic inactivation of SMARCB1, a gene encoding a SWI/SNF complex subunit, causes pediatric rhabdoid tumors (RTs). These highly aggressive soft tissue tumors occur in infants and young children and have extremely poor outcomes. Since RT genomes are diploid and lack other mutations, they are ideal for studying SWI/SNF-specific mechanisms driving cancer and for identifying novel therapeutic targets. My mentor and his collaborators initiated the Pediatric Cancer Dependency Project to identify novel drivers and therapeutic targets in pediatric cancers, including RT. Performing genome-wide CRISPR screens in 10 RT cell lines compared to over 800 other cancer cell lines revealed a novel gene that SMARCB1-deficient RT specifically depend upon for survival. This proposal seeks to investigate the function of this putative chromatin regulator and to determine why it constitutes a specific dependency in RT. Overexpression of this gene is associated with poor prognosis in several cancers and thus pharmacological efforts are already underway to develop chemical inhibitors. Intriguingly, preliminary experiments suggest that this protein may control histone post-translational modifications (PTMs) that dictate remodeling by SWI/SNF complexes and gene expression. Understanding why RT cells depend on this protein for survival will reveal novel mechanisms of chromatin regulation and may identify a new therapeutic target in these lethal cancers. My central hypothesis is that this protein controls histone PTMs and is required for the chromatin recruitment of the sole family of SWI/SNF complexes that lack SMARCB1, thus making it essential in RT. This proposal will investigate how this regulator, which lacks enzymatic activity, controls these histone PTMs and how this influences chromatin accessibility. Additionally, it will determine how this regulator influences remodeling and gene expression controlled by SWI/SNF complexes. Collectively, this proposal will uncover the function of this relatively understudied protein, provide novel insight into how chromatin function is regulated, explain why RTs selectively depend on this protein for survival, and potentially identify a novel therapeutic target in the lethal pediatric rhabdoid tumor. Additionally, this proposal is designed to address my training goal of becoming proficient in studying chromatin biology both experimentally and computationally.