ATP-Dependent Chromatin Remodeling in Human Malignancy

人类恶性肿瘤中 ATP 依赖性染色质重塑

• 批准号: 8371602
• 负责人: Gerald R. Crabtree
• 金额: $ 32.65万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-10 至 2017-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8371602
• 关键词: Accounting; Acute; Affect; Alleles; Anaphase; Aneuploidy; Antibodies; Automobile Driving; Binding; Biochemical; Brain; Breast; Catenated DNA; Cell Cycle Progression; Cell Nucleus; Cells; ChIP-seq; Chimeric Proteins; Chromatin; Chromatin Structure; Common Neoplasm; Complex; DNA; Data; Databases; Dependence; Development; Drops; Event; Failure; Frequencies; Functional disorder; Funding; Gene Family; Gene Targeting; Genes; Genome; Grant; Growth; Human; Impairment; In Vitro; Individual; Kidney; Knowledge; Laboratories; Lead; Light; Lung; Malignant - descriptor; Malignant Neoplasms; Maps; Mitosis; Mitotic; Molecular; Molecular Probes; Mutate; Mutation; Oncogenic; Ovary; Phenotype; Polycomb; Proteins; Role; SMARCA2 gene; SMARCB1 gene; SMARCC1 gene; Site; Solutions; Tail; Tertiary Protein Structure; Time; Tissues; Topoisomerase; Topoisomerase II; Tumor Suppressor Proteins; Work; X Chromosome; cell type; chromatin remodeling; defined contribution; exome; gain of function; genome-wide; inhibitor/antagonist; insight; integrase interactor 1; loss of function mutation; medulloblastoma; member; mutant; neoplastic cell; novel; novel therapeutics; overexpression; pluripotency; prevent; restraint; sarcoma; small molecule; synovial sarcoma; tumor; tumorigenesis

DESCRIPTION (provided by applicant): Recent screens for driving mutations in human malignancy have repeatedly identified subunits of mammalian SWI/SNF-like BAF complexes as tumor suppressors. Biochemical studies indicate that the identified subunits: BAF250a, Brg (BAF190), BAF155, BAF60b, BAF53a, and BAF47 (hSNF5) are dedicated to these complexes and not found as individual proteins or as parts of other complexes. In addition, we have recently found that SS18 (mutated in Synovial Sarcoma), Bcl7 and Bcl11 appear to be dedicated, stable subunits of BAF complexes. These studies suggest that SWI/SNF-like BAF complexes might be one of the most commonly mutated chromatin regulators in human cancer. BAF complexes regulate chromatin structure and are composed of about 14 subunits that are combinatorially assembled from the products of gene families encoding the subunits. The mechanisms underlying their frequent mutation in cancer are unclear. We have found that conditional deletion or depletion of the oncogenic subunits leads to stalling in mitosis and anaphase bridge formation, strongly implicating a failure to decatenate DNA during M phase. Importantly, Topoisomerase IIa (Topo IIa), which resolves catenated DNA at M phase associates with BAF complexes and Brg is essential for chromatin binding by Topo IIa. Furthermore, purified BAF complexes are required for optimal decatenation by purified Topo IIa in vitro. These observations suggest that a failure of decatenation by Topo IIa contributes to the genesis of human cancers, which is the central hypothesis of this application. This hypothesis is supported by the high frequency of concurrent mutations in other genes or aneuploidy in tumors bearing apparent initiating mutations in BAF subunits. To study these oncogenic BAF mutations, the SS18 translocation to SSX is particularly useful since it produces a sterotypic in-frame fusion of the SS18 BAF subunit to a member of the SSX gene family located on the X chromosome. This precise translocation attaches 78aa of SSX to SS18 and is almost certainly the driving event in synovial sarcoma (SS), which account for about 8% of sarcomas. Remarkably, the translocation of one allele leads to partial dissolution of BAF complexes. We will begin our studies by determining whether the SS18-SSX fusion causes a loss or gain of function for BAF complexes. We will define the consequences of this translocation for BAF complex binding over the genome to determine if target genes are lost or gained. We will then determine why the wildtype SS18 allele is repressed and leads to the formation of little protein compared to the translocated allele. We will examine the potentially oncogenic role of Topo IIa's dependence upon BAF complexes. Finally, we will attempt to understand how activating mutations in a- catenin and PI3K apparently cooperate with loss-of-function mutations in BAF subunits to lead to cancer. At the conclusion of our work we expect to have gained insight into the mechanism of transformation by mutations of the subunits of BAF complexes, which are emerging as major contributors to human cancer. PUBLIC HEALTH RELEVANCE: Recent studies have found that many human tumors, including common tumors of the brain, lung, breast, ovary and kidney harbor mutations within the subunits of a complex that uses energy provided by ATP to control the packaging and unpackaging of DNA in the nucleus. These BAF complexes unveil genes for their expression at specific times in development and in specific tissues. At present there is only rudimentary knowledge of the function of these complexes in human cells. Furthermore, it is not known how the mutations affect the normal functions of the complexes and how they cause cells to become malignant. Our studies will shed light upon the molecular mechanisms involved in tumor formation and open new therapeutic strategies for control of specific cancers.

描述（由申请人提供）：最近用于驱动人类恶性肿瘤突变的筛选已多次鉴定出哺乳动物 SWI/SNF 样 BAF 复合物的亚基作为肿瘤抑制因子。生化研究表明，已鉴定的亚基：BAF250a、Brg (BAF190)、BAF155、BAF60b、BAF53a 和 BAF47 (hSNF5) 专用于这些复合物，而不是作为单个蛋白质或作为其他复合物的一部分被发现。此外，我们最近发现 SS18（在滑膜肉瘤中突变）、Bcl7 和 Bcl11 似乎是 BAF 复合物的专用、稳定亚基。这些研究表明，SWI/SNF 样 BAF 复合物可能是人类癌症中最常见的突变染色质调节因子之一。 BAF 复合物调节染色质结构，由约 14 个亚基组成，这些亚基由编码亚基的基因家族的产物组合组装而成。它们在癌症中频繁突变的机制尚不清楚。我们发现，致癌亚基的条件性删除或耗尽会导致有丝分裂和后期桥形成的停滞，强烈暗示在 M 期期间未能连接 DNA。重要的是，拓扑异构酶 IIa (Topo IIa) 可解析 M 期的连锁 DNA，与 BAF 复合物和 Brg 结合，对于 Topo IIa 染色质结合至关重要。此外，纯化的 Topo IIa 体外最佳去连接需要纯化的 BAF 复合物。这些观察结果表明，Topo IIa 的串联失败会导致人类癌症的发生，这是本申请的中心假设。其他基因中的高频率并发突变或 BAF 亚基中具有明显起始突变的肿瘤中的非整倍性支持了这一假设。为了研究这些致癌 BAF 突变，SS18 易位至 SSX 特别有用，因为它产生 SS18 BAF 亚基与位于 X 染色体上的 SSX 基因家族成员的定型框内融合。这种精确的易位将 SSX 的 78 个氨基酸连接到 SS18，并且几乎肯定是滑膜肉瘤 (SS) 的驱动事件，滑膜肉瘤约占肉瘤的 8%。值得注意的是，一个等位基因的易位导致 BAF 复合物部分溶解。我们将通过确定 SS18-SSX 融合是否导致 BAF 复合物功能丧失或增强来开始我们的研究。我们将定义 BAF 复合物在基因组上结合的这种易位的后果，以确定目标基因是否丢失或获得。然后我们将确定为什么野生型 SS18 等位基因受到抑制并导致与易位等位基因相比形成很少的蛋白质。我们将研究 Topo IIa 对 BAF 复合物的依赖性的潜在致癌作用。最后，我们将尝试了解 a-连环蛋白和 PI3K 的激活突变如何与 BAF 亚基的功能丧失突变协同作用，从而导致癌症。在我们的工作结束时，我们希望能够深入了解 BAF 复合物亚基突变的转化机制，这些亚基正在成为人类癌症的主要贡献者。 公共健康相关性：最近的研究发现，许多人类肿瘤，包括脑、肺、乳腺癌、卵巢和肾的常见肿瘤，在利用 ATP 提供的能量来控制细胞核中 DNA 的包装和解包的复合物的亚基内存在突变。这些 BAF 复合物揭示了它们在发育的特定时间和特定组织中表达的基因。目前，人们对这些复合物在人体细胞中的功能仅了解初步的知识。此外，尚不清楚突变如何影响复合物的正常功能以及它们如何导致细胞恶性。我们的研究将揭示肿瘤形成的分子机制，并为控制特定癌症开辟新的治疗策略。