T-DNA INTEGRATION DURING CROWN GALL TUMORIGENESIS

在冠瘿肿瘤发生过程中， 根癌农杆菌肿瘤诱导（Ti）质粒，称为 T-DNA整合到植物的核DNA中。 类似23基地- 在T区的每个末端的一对（bp）直接重复序列发出T- DNA边界。 T-DNA传递（转移和整合） 只需要顺式的右手重复序列，但需要24 bp的序列， 通常在右侧重复， 刺激这个过程。 虽然右边界重复功能 最好在一个方向，过量功能在任何方向。 为了了解T-DNA传递的机制，我们将 研究在T-DNA过程中形成的分子中间体 传输和确定角色的边界和边界 在他们的阵型中重复比赛。 通过基因和 我们将通过生物化学实验， 这些序列。 为了了解它的行为，我们将 检查其位置对刺激T细胞的能力的影响， DNA边界功能 为了研究分子机制， T-DNA整合到植物DNA中，我们将描述 在T-DNA整合过程中宿主DNA发生的变化。 我们的实验将有助于了解独特的， 细菌之间发生重要重组事件 和宿主DNA在冠瘿肿瘤发生过程中， 改进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的方法， 在动物中的病毒肿瘤诱导。 了解机制 T-DNA整合的机制也可能揭示 腺病毒整合，这一过程可能涉及类似 分子事件 土壤杆菌和立克次氏体（细菌 引起战壕热Q热和落基山斑疹伤寒 人类发烧）有着相似的生活方式（密切相关 与真核宿主细胞和质粒相关， 毒力）以及非常接近的系统发育关系。 因此，A.根瘤菌可以作为立克次体的模型 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, 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.