INTERACTIONS BETWEEN DNA AND THE LYSR-TYPE PROTEIN OCCR

摘要对植物根癌农杆菌的转化过程进行了深入的研究。 现象，是自然遗传的唯一真正的例子 工程学。感染细菌将其DNA片段 从一个肿瘤诱导(钛)质粒，进入宿主植物基因组。基因 编码在该片段上的直接肿瘤形成和合成 不同寻常的糖和氨基酸被称为Opines，它们的作用是 农杆菌特有的碳/氮源。反过来，这些观点 刺激根癌农杆菌参与其基因的表达 钛质粒的摄取和利用，结合转移，以及 可能与肿瘤定植有关的其他功能。 在章鱼碱类型的质粒中，这种诱导至少部分地通过 LysR-型转录激活子OccR，它诱导 这些基因的转录对阿片章鱼的反应 也会自动调节自身的合成。OCCR的目标之一 调控是重叠的、不同转录的启动子区域 在OCC(章鱼分解代谢)操纵子和occR基因本身之间。 这种不寻常的遗传组织是LysR类型系统的典型特征 可能允许同时控制两个操纵子。在建议的 研究，我们将研究OCCR与此的相互作用 转录控制区。提出了OccR结合的证据 在章鱼存在或不存在的情况下， 诱导Occr和/或其靶点的构象变化。我们 假设；i)OccR弯曲其目标位置，即章鱼刺激 这种弯曲的调制，并且这些变化导致 转录诱导，或ii)章鱼碱诱导构象 OccR本身的变化会导致转录激活。这个 拟议的调查将利用生化、分子生物学、 以及检验这些假说的基因技术。

The process of Agrobacterium tumefaciens of plants is a well studied phenomenon, and is the only bonafide example of natural genetic engineering. The infecting bacterium transfers a fragment of its DNA from a tumor inducing (Ti) plasmid, into the host plant genome. Genes encoded on this fragment direct tumor formation and the synthesis of unusual sugars and amino acids termed opines, which serve as Agrobacterium-specific carbon/nitrogen sources. In turn, the opines stimulate the expression of A. tumefaciens genes involved in their uptake and utilization, conjugal transfer of the Ti plasmid, and a number of other functions that may be involved in tumor colonization. In octopine-type plasmids this induction is mediated at least in part by the LysR-type transcriptional activator OccR, which induces the transcription of these genes in response to the opine octopine and which also autoregulates its own synthesis. One of the targets for OccR regulation is the overlapping, divergently transcribed promoter region between the occ (octopine catabolism) operon and the occR gene itself. This unusual genetic organization is typical of LysR-type systems and probably allows simultaneous control of both operons. In the proposed study, we shall examine the interaction of OccR with this transcriptional control region. Evidence is presented that OccR binds to this region in the presence or absence of octopine, and that octopine induces conformational changes in Occr and/or its target site. We hypothesize that; i) OccR bends its target site, that octopine incites modulation of this bending, and that these changes result in the induction of transcription, or ii) that octopine-induced conformational changes in OccR itself result in transcriptional activation. The proposed investigation will employ biochemical, molecular biological, and genetic techniques to test these hypotheses.