Isolation and characterization of plant insulators

绝缘子是能够阻断不适当或不需要的增强子-启动子通讯（增强子阻断活性）和/或阻止抑制性染色质向活性染色质扩散（屏障活性）的DNA元件。它们的作用由识别它们的蛋白质介导，导致许多蛋白质的招募，并最终组装“绝缘体”，即所谓的“功能单位”。因此，绝缘子代表了一个额外的转录控制水平，它们的研究为理解基因调控的基本、普遍机制提供了机会。

Insulators are DNA elements that are able to block inappropriate or unwanted enhancer-promoter communication (enhancer blocker activity) and/or prevent the spread of repressive chromatin into active chromatin (barrier activity). Their action is mediated by protein(s) that recognize them leading to the recruitment of many proteins and ultimately the assembly "insulator bodies" the proposed "functional unit". Thus insulators represent an additional level of transcriptional control and their study represents an opportunity to understand a basic, universal mechanism of gene regulation. Insulators from number of species have been identified including fungi, yeast, fruit fly, chicken and human but not plant. Our work indicated that in Arabidopsis two insulators, UASrpg and BEAD-1C can function as insulators-first published demonstration of insulator activity in a plant. Given the potential importance of insulators in plant gene expression and possible key roles in plant biotechnology for the control of tissue-specific transgene expression, we have embarked on a research programme to isolate and study plant insulators. Our approach is to avoid the use of candidate sequences and to tackle the problem by adapting our transgenic system for the direct selection of DNA elements with insulating activity. Sequence(s) thus isolated can be cloned into other vectors to eliminate insulators that are not functional in a variety of promoter/enhancer combinations, orientation and a range of different species. With such sequences in hand we can devise means to isolate the proteins that recognize them and test models of insulator activity proposed for animal systems. Our long term goal is to understand how these interactions regulate gene expression in plants and their evolution. In addition a function and universal plant insulator would have an impact on the design of a new generation of plant transformation vectors.