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: 9054819
• 负责人: Gerald R. Crabtree
• 金额: $ 32.89万
• 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/9054819
• 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; DNA topoisomerase II alpha; 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; Tail; Tertiary Protein Structure; Time; Tissues; Topoisomerase II; Tumor Suppressor Proteins; Work; X Chromosome; cell type; chromatin remodeling; defined contribution; exome sequencing; gain of function; genome-wide; insight; loss of function mutation; medulloblastoma; member; mutant; neoplastic cell; novel; novel therapeutic intervention; overexpression; pluripotency; prevent; restraint; sarcoma; small molecule; small molecule inhibitor; 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.

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反复鉴定出哺乳动物SWI/SNF样BAF复合物的亚基为肿瘤抑制剂。生化研究表明，已鉴定的亚基：BAF250A，BRG（BAF190），BAF155，BAF60B，BAF53A和BAF47（HSNF5）（HSNF5）专用于这些复合物，而不是作为单个蛋白或其他复合物的各个部分。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，稳定的亚基。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染色质调节剂之一。 BAF复合物调节染色质结构，由大约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合。其在癌症中频繁突变的基础机制尚不清楚。我们发现，致癌亚基的条件缺失或耗竭会导致有丝分裂和后期桥的形成停滞，这强烈暗示在M期未能脱发DNA。重要的是，拓扑异构酶IIA（TOPO IIA）在与BAF复合物和BRG的M相缔合中分解的DNA对于Topo IIA的染色质结合至关重要。此外，纯化的BAF复合物是在体外纯化的Topo IIA所必需的。这些观察结果表明，Topo IIA的衰老失败有助于人类癌的起源，这是该应用的核心假设。该假设得到了其他基因中的高频突变或非整倍性在BAF亚基中明显启动突变的肿瘤中的频率。为了研究这些致癌性BAF突变，SS18转移到SSX特别有用，因为它会产生SS18 BAF亚基的固定型内融合到位于X染色体上的SSX基因家族成员。这种精确的易位将SSX的78AA连接到SS18，几乎可以肯定是滑膜肉瘤（SS）的驾驶事件，该事件约占肉瘤的8％。值得注意的是，一个等位基因的易位导致BAF复合物的部分溶解。我们将通过确定SS18-SSX融合是否会导致BAF复合物的功能损失或增益来开始我们的研究。我们将定义这种易位对基因组上BAF复合物结合的后果，以确定靶基因是否丢失或获得。然后，我们将确定为什么野生型SS18等位基因被抑制，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，我们将尝试了解如何激活A-Catenin和PI3K中的突变，显然与BAF亚基的功能丧失突变合作以导致癌症。在工作结束时，我们期望通过BAF复合物的亚基突变的突变来深入了解转化的机理，而BAF复合物的亚基成为了人类癌症的主要贡献者。