Molecular and Genetic Studies on Maize Elements

玉米中ac转座子的功能受其自身产物转座酶的控制，转座酶作为一种反式激活蛋白，导致玉米处于稳定状态。Ac的激活与启动子区域的去甲基化有关。在一项旨在确定启动子去甲基化的分子基础的研究中，将使用结构改变的、有缺陷的ac元件，这些元件在转座酶对其启动子的去甲基化过程中存在差异。该项目的第二部分涉及分析反兴奋剂系统各要素之间的远程顺位相互作用。当Ac和DS元件连接在同一染色体臂上时，远端元件发生甲基化，不会被甲基酶敏感的限制性内切酶消化。这种效应仅限于连接在同一染色体臂上的元素，但它们之间的距离可能长达50个图谱单位。将构建许多不同的ac、ds和其他标记基因的双重和三重组合，以研究这种长距离顺式相互作用的性质。在之前NSF支持的一段时间里，这项建议的作者发现，一个基因可以影响同一染色体上另一个基因的行为，影响的距离比之前想象的要远得多。他现在提议继续这一发现，并试图阐明基因之间发生这种远程相互作用的机制。

The functioning of the Ac transposable element in maize is controlled by its own product, transposase, that acts as a transactivating protein resulting in a steady state condition. Activation of Ac is associated with the demethylation of the promoter region. Structurally altered, defective Ac elements that differ in the demethylation of their promoter by transposase will be employed in a study designed to determine the molecular basis for the promoter demethylation. The second part of this project involves an analysis of the long range cis interaction between elements of the Ac-Ds system. When an Ac and a Ds element are coupled on the same chromosome arms, the distal element becomes methylated and is not digested by methylase-sensitive restriction enzymes. This effect is limited to elements coupled on the same chromosome arm, but they may be as far apart as 50 map units. Many different double and triple combinations of Ac, Ds and other marker genes will be constructed to study the nature of this long range cis interaction. During a period of previous NSF support, the author of this proposal has discovered that one gene can influence the behavior of another gene on the same, chromosome over much greater distances than previously imagined. He now proposes to pursue this discovery, and attempt to elucidate the mechanism by which such long-range interactions among genes occur.