Temporal and Spatial Control of V(D)J Recombination

描述(由申请人提供)：儿童在15岁之前有1/2000的几率患上白血病。最常见的儿童白血病类型通常表现为严重的染色体异常。虽然人们了解其中一些异常的后果，但对于这些基因组错位是如何发生的，或者环境因素如何影响它们的发生频率，我们知道的要少得多。与肿瘤相关的染色体异常是由不稳定的DNA交易引起的，包括V(D)J重组，这是一种程序性DNA重排形式，通常用于组装抗原受体基因。在初步工作中，我们定义了在时间和空间上限制V(D)J重组的分子机制，并进一步证明了错误的重组与基因组不稳定和淋巴肿大有关。在这些成就的基础上，这项建议下提出的工作旨在从机制上理解白血病前体细胞的基因组不稳定性，建立新的工具来揭示严重染色体异常和协同突变之间的功能相互作用，并通过限制V(D)J重组酶活性的不稳定效应来确定可能保护基因组的表观遗传学机制。在第一个目标下，我们将阐明重组酶活性的翻译后调节在发育中的淋巴细胞中加强基因组完整性的机制。这一目标特别重要，因为它是意料之中的 阐明在白血病和其他恶性肿瘤中启动染色体重排的机制。在第二个目标下，我们将利用与非计划V(D)J重组相关的基因组可塑性来确定染色体易位和较小的遗传损伤之间的淋巴生成相互作用。第三个目标将定义一种特定的机制，通过该机制，染色质的转录激活将V(D)J重组限制在正常和异常发育过程中的特定位置。因此，这项建议的首要主题是阐明在发育中的淋巴细胞中控制基因组可塑性的机制，并确定这些控制和对淋巴样癌的内在防御之间的关系。 公共卫生相关性：淋巴细胞癌是儿童时期最常见的威胁生命的疾病之一。染色体DNA的异常重排导致了大多数癌症的发生。该项目下的工作将有助于为了解这些异常重排是如何发生的提供一个框架，并最终可能导致预测、诊断和治疗的新方法。

DESCRIPTION (provided by applicant): A child has a 1 in 2000 chance of developing leukemia by the age of 15. The most common types of childhood leukemia typically exhibit gross chromosomal abnormalities. While the consequences of some of these abnormalities are understood, much less is known about how these genomic derangements occur in the first place, or how environmental factors affect the frequency of their occurrence. Tumor-associated chromosomal aberrations result from destabilizing DNA transactions, including V(D)J recombination, a form of programmed DNA rearrangement that normally serves to assemble antigen receptor genes. In preliminary work we have defined molecular mechanisms that constrain V(D)J recombination in time and in space, and have proceeded to demonstrate that mistimed recombination is associated with genomic instability and lymphomagenesis. Building on these accomplishments, the work proposed under this proposal aims to develop a mechanistic understanding of genomic instability in leukemic progenitors, to build new tools to uncover functional interactions between gross chromosomal abnormalities and cooperating mutations, and to define epigenetic mechanisms that may protect the genome by limiting the destabilizing effects of V(D)J recombinase activity. Under the first aim we will elucidate mechanisms by which posttranslational regulation of recombinase activity enforces genomic integrity in developing lymphoid cells. This aim is of particular importance because it is expected to shed light on mechanisms that initiate chromosomal rearrangements in leukemias and other malignancies. Under the second aim we will exploit the genomic plasticity associated with unscheduled V(D)J recombination to identify lymphomagenic interactions between chromosomal translocations and smaller genetic lesions. The third aim will define a specific mechanism by which the transcriptional activation of chromatin constrains V(D)J recombination to particular sites during normal and abnormal development. Thus the overarching themes of this proposal are to elucidate mechanisms that control genomic plasticity in developing lymphoid cells and to determine the relationships between these controls and intrinsic defenses against lymphoid cancer. PUBLIC HEALTH RELEVANCE: Cancers of lymphoid cells are among the most common life-threatening diseases of childhood. Abnormal rearrangements of chromosomal DNA contribute to the development of most of these cancers. Work under this project will help provide a framework for understanding how these abnormal rearrangements occur and may ultimately lead to novel methods for prediction, diagnosis and treatment.