T-DNA INTEGRATION DURING CROWN GALL TUMORIGENESIS

在根癌发生过程中， 根癌农杆菌肿瘤诱导（Ti）质粒，称为T-DNA，整合到 植物核DNA 相似的23个碱基对（bp）的直接重复在每个末端的 T区是T-DNA边界的信号。 T-DNA传输（转移和 整合）只需要顺式的右手重复，但24 bp的 一个序列，称为重复序列，它通常在右侧重复很大 刺激这个过程。 虽然右边界重复功能最好在一个 方向，则在任一方向上均起作用。 了解 T-DNA传输机制，我们将研究分子 在T-DNA传递过程中形成并决定作用的中间体 在他们的阵型中，边后卫和边后卫重复出场。 通过基因 和生物化学实验，我们将确定蛋白质， 这些序列。 为了了解它是如何起作用的，我们将检查 其位置对刺激T-DNA边界功能的能力的影响。 研究T-DNA整合到植物中的分子机制 DNA，我们将描述在T-DNA期间宿主DNA中发生的变化 一体化 我们的实验将有助于了解独特的和重要的 细菌和宿主DNA之间发生的重组事件， 胆囊肿瘤发生，他们将改善T-DNA作为模型系统， 研究肿瘤发生、基因表达和宿主-病原体相互作用。 这项研究将确定肿瘤建立所需的因素， 可能提示阻断肿瘤发生的方法，这是一个重要的目标， 冠瘿肿瘤发生和病毒肿瘤诱导之间的相似性， 动物 了解T-DNA整合的机制也可能有助于 腺病毒整合的机制，一个过程， 涉及类似的分子事件。 土壤杆菌和立克次氏体（细菌 引起战壕热、Q热和落基山斑疹热， 人类）共享生活方式的相似性（与真核生物密切相关） 宿主细胞和与毒力相关的质粒），除了非常 亲缘关系密切。 因此，A.根瘤菌可以作为一个模型 立克次氏体发病机制以及人类肿瘤发生。

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, overdrive 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 exmine the effect 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, an important goal given the similarities between crown gall 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 molecule 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.