Temporal and Spatial Control of V(D)J Recombination

描述（由申请人提供）：儿童在15岁时患白血病的几率为1/2000。最常见的儿童白血病类型通常表现出明显的染色体异常。虽然这些异常的后果已经被理解，但对于这些基因组紊乱首先是如何发生的，或者环境因素如何影响其发生频率，我们知之甚少。肿瘤相关的染色体畸变由不稳定的DNA转换引起，包括V（D）J重组，一种通常用于组装抗原受体基因的程序性DNA重排形式。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，并进一步证明了错时重组与基因组不稳定性和淋巴瘤发生有关。在这些成就的基础上，本提案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染色体异常和协同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节在淋巴样细胞发育中加强基因组完整性的机制。这一目标特别重要，因为人们期望 阐明白血病和其他恶性肿瘤中染色体重排的启动机制。在第二个目标下，我们将利用与非程序性V（D）J重组相关的基因组可塑性来鉴定染色体易位和较小遗传病变之间的淋巴瘤发生相互作用。第三个目标将定义一种特定的机制，通过这种机制，染色质的转录激活将V（D）J重组限制在正常和异常发育期间的特定位点。因此，这一建议的首要主题是阐明机制，控制基因组可塑性在发展中的淋巴细胞，并确定这些控制和内在防御淋巴癌之间的关系。

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.