PHYSICAL CHEMISTRY OF RECOMBINATIONAL INTERMEDIATES

基因重组普遍存在于生物体内，从 病毒传染给人类。重组的基本特征是相互作用 以产生新的遗传物质，这种物质可能在物理上 结合两个相互作用分子的片段。其后果是 这些变化包括病毒在不同物种中的整合 原核生物中的噬菌体对人类体内的逆转录病毒，如艾滋病毒。 基因转位，具有临床后果的基因复制， 免疫系统的发展和人类基因的多样化 通过减数分裂交叉的水池都是重组过程的结果。 重组不仅仅是一种被动的现象：最近，它已经成为 遗传学家广泛使用的一种工具，用来修改 实验物种。 这项工作的目标是理解结构、动力学和 参与基因重组的DNA分子的热力学。脱氧核糖核酸 可以在实验室中设计和综合的模型系统有 强调。这些分子中的关键是Holliday连接，它 是一种四链支链重组中间体。一直以来 最近由不对称模拟分子模拟，已经发现 具有不对称的双域反平行结构；而这 这一发现意味着不对称的遗传产物是序列的函数 分支，它将确定分子是否具有自然对称性 也具有不对称的结构域结构。平行或反平行 作为拆分酶底物的中间体的性质 也可以用连接的分子来建立。霍利迪交汇处 经历两种具有遗传后果的异构化，在 区域结构和分支点的迁移；乘积 这些异构化与基因的结果直接相关 重组。万圣节的连锁版和打结版 中间体将被用来探索和控制这些异构化。 我们将尝试确定这座城市的三维结构 通过结晶学的中间体。 打结的DNA分子也是重组的中间体。它是 有可能构建合成DNA结的模型，其物理性质 属性将被确定。结包含固定的节点结构， 它将被用来确定DNA的节点特异性 拓扑异构酶。此外，它们的拓扑属性使 对DNA的自然扭曲应力状态进行建模。这些不同寻常的 DNA结构将被用来寻找识别 它们是独一无二的，或者它们是同源的底物。 即将进行的研究将回答有关DNA的关键问题 参与重组的分子。它将产生混凝土 关于这些不寻常的DNA分子的结构和物理知识。这个 最终目标是提供对自然重组的分子控制 现象和今天在美国进行的重组干预 实验室，明天在诊所。

Genetic recombination occurs universally in living organisms, from viruses to humans. The basic feature of recombination is the interaction of two pieces of DNA to yield new genetic material that may physically incorporate segments of both interacting molecules. The consequences of these changes include viral integration in species ranging from bacteriophages in prokaryotes to retroviruses, such as HIV, in humans. Genetic transposition, gene duplications with clinical consequences, the development of the immune system, and the diversification of human gene pools through meiotic crossovers all result from recombination processes. Recombination is not just a passive phenomenon: Recently, it has become a tool used extensively by geneticists to modify the genes of experimental species. The goals of this work are to understand the structure, dynamics and thermodynamics of DNA molecules involved in genetic recombination. DNA model systems that can be designed and synthesized in the laboratory are emphasized. Key among these molecules is the Holliday junction, which is a four-stranded branched recombination intermediate. It has been modeled recently by asymmetric analog molecules, which have been found to have asymmetric two-domain antiparallel structures; whereas this finding implies asymmetric genetic products as a function of sequence at the branch, it will be determined whether molecules with natural symmetry also have asymmetric domain structures. The parallel or antiparallel nature of the intermediate as a substrate for resolution enzymes will also be established, using catenated molecules. Holliday junctions undergo two isomerizations with genetic consequences, switching between domain structures and migration of the branch point; the products of these isomerizations are directly related to the genetic results of recombination. Catenated and knotted versions of the Holliday intermediate will be used to explore and control, these isomerizations. Attempts will be made to determine the three-dimensional structure of the intermediate by crystallography. Knotted DNA molecules are also recombination intermediates. It is possible to construct model synthetic DNA knots, whose physical properties will be determined. Knots contain fixed node-structures, which will be used to determine the nodal specificities of DNA topoisomerases. In addition, their topological properties enable modeling the natural, torsionally-stressed state of DNA. These unusual DNA structures will be used to seek cellular activities that recognize them uniquely, or for which they are cognate substrates. The research to be performed will answer key questions about the DNA molecules that are involved in recombination. It will yield concrete structural and physical knowledge about these unusual DNA molecules. The ultimate goal is to provide molecular control over natural recombination phenomena and over recombinational interventions done today in the laboratory and tomorrow in the clinic.