Temporal and Spatial Control of V(D)J Recombination

描述（由申请人提供）：儿童在15岁前患白血病的几率为1 / 2000。最常见的儿童白血病类型通常表现为明显的染色体异常。虽然我们已经了解了其中一些异常的后果，但对于这些基因组紊乱最初是如何发生的，以及环境因素是如何影响其发生频率的，我们所知甚少。肿瘤相关的染色体畸变是由不稳定的DNA交易引起的，包括V(D)J重组，这是一种程序化的DNA重排形式，通常用于组装抗原受体基因。在初步工作中，我们已经确定了在时间和空间上限制V(D)J重组的分子机制，并进一步证明了不合时宜的重组与基因组不稳定性和淋巴瘤发生有关。在这些成果的基础上，本提案下提出的工作旨在发展对白血病祖细胞基因组不稳定性的机制理解，建立新的工具来揭示总体染色体异常和合作突变之间的功能相互作用，并定义可能通过限制V(D)J重组酶活性的不稳定作用来保护基因组的表观遗传机制。在第一个目标下，我们将阐明重组酶活性的翻译后调控在发育中的淋巴样细胞中加强基因组完整性的机制。这一目标特别重要，因为它是预期的

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.