T-DNA INTEGRATION DURING CROWN GALL TUMORIGENESIS

在冠胆肿瘤形成过程中，特定的一段 根癌农杆菌肿瘤诱导(Ti)质粒，称为 T-DNA，整合到植物核DNA中。相似的23个碱基- 在T区两端的直接重复序列对(BP)表示T- DNA边界。T-DNA传递(转移和整合) 只需要顺式序列中的右侧重复序列，但需要24个碱基的序列， 被称为超速，通常在右侧重复很多 刺激了这一过程。尽管右边框重复功能 在一个方向上最好，在任何一个方向上都有过量作用。 为了了解T-DNA的传播机制，我们将 检测T-DNA过程中形成的分子中间体 传递和确定角色的超速和边界 在他们的队形中重复演奏。通过遗传和 生物化学实验我们将识别相互作用的蛋白质 有了这些序列。为了了解超速驾驶是如何运作的，我们将 研究其位置对刺激T细胞的能力的影响 DNA边界功能。通过以下方法来研究分子机制 哪些T-DNA整合到植物DNA中，我们将表征 T-DNA整合过程中宿主DNA发生的变化。 我们的实验将有助于理解独特的和 细菌之间发生的重要重组事件 和宿主DNA在冠胆肿瘤发生过程中，它们将 完善T-DNA作为研究的模型系统 肿瘤发生、基因表达和宿主-病原体相互作用。 这项研究将确定肿瘤所需的因素 建立并可能提出阻止肿瘤发生和 病毒在动物体内诱发肿瘤。对机制的理解 T-DNA整合的研究也可能有助于阐明 腺病毒整合，这一过程可能涉及类似的 分子事件。农杆菌和立克次体(细菌 引起战壕热、Q热和落基山斑点 人类发烧)有相似的生活方式(密切相关 与真核宿主细胞和与之相关的质粒 毒力)，此外还有非常密切的系统发育关系。 因此，根癌农杆菌可作为立克次体的模型。 发病机制以及人类肿瘤的发生。

During crown gall tumorigenesis a specific segment of the Agrobacterium tumefaciens tumor-inducing (Ti) plasmid, called the T-DNA, integrates into plant nuclear DNA. Similar 23 base- pair (bp) direct repeats at each end of the T region signal the T- DNA borders. T-DNA transmission (transfer and integration) requires only the right-hand repeat in cis, but a 24 bp sequence, called overdrive, which normally flanks right repeats greatly stimulates the process. Although right border repeats function best in one orientation, overdose functions in either orientation. To understand the mechanism of T-DNA transmission, we will examine the molecular intermediates which form during T-DNA transmission and determine the roles overdrive and the border repeats play in their formation. Through genetic and biochemical experiments we will identify proteins which interact with these sequences. To understand how overdrive acts, we will examine the effects of its location on the ability to stimulate T- DNA border function. To examine the molecular mechanism by which T-DNA integrates into plant DNA, we will characterize changes that occur in host DNA during T-DNA integration. Our experiments will contribute to understanding the unique and important recombination events that occur between bacterial and host DNA during crown gall tumorigenesis, and they will improve the T-DNA as a model system for studying tumorigenesis, gene expression, and host-pathogen interactions. This research will identify factors required for tumor establishment and may suggest ways to block tumorigenesis and viral tumor induction in animals. Understanding the mechanism of T-DNA integration may also shed light on the mechanism of adenovirus integration, a process that may involve similar molecular events. Agrobacterium and rickettsiae (bacteria which cause trench fever, Q fever, and Rocky Mountain spotted fever in humans) share lifestyle similarities (close association with eukaryotic host cells and plasmids associated with virulence) in addition to a very close phylogenetic relationship. Thus, A. tumefaciens may serve as a model for rickettsial pathogenesis as well as human tumorigenesis.