Bondarenko Vladimir A, Jiang Yong I, Studitsky Vasily M
Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, 540 East Canfield Avenue, Room 5123, Detroit, MI 48201, USA.
EMBO J. 2003 Sep 15;22(18):4728-37. doi: 10.1093/emboj/cdg468.
Insulators are DNA sequences that are likely to be involved in formation of chromatin domains, functional units of gene expression in eukaryotes. Insulators can form domain boundaries and block inappropriate action of regulatory elements (such as transcriptional enhancers) in eukaryotic nuclei. Using an in vitro system supporting enhancer action over a large distance, the enhancer-blocking insulator activity has been recapitulated in a highly purified system. The insulator-like element was constructed using a sequence-specific DNA-binding protein making stable DNA loops (lac repressor). The insulation was entirely dependent on formation of a DNA loop that topologically isolates the enhancer from the promoter. This rationally designed, inducible insulator-like element recapitulates many key properties of eukaryotic insulators observed in vivo. The data suggest novel mechanisms of enhancer and insulator action.
绝缘子是一种DNA序列，可能参与染色质结构域的形成，而染色质结构域是真核生物基因表达的功能单位。绝缘子可以形成结构域边界，并阻止真核细胞核中调控元件（如转录增强子）的不当作用。利用一个支持增强子远距离作用的体外系统，在一个高度纯化的系统中重现了增强子阻断绝缘子活性。使用一种能形成稳定DNA环的序列特异性DNA结合蛋白（乳糖阻遏物）构建了类似绝缘子的元件。绝缘完全依赖于DNA环的形成，该环在拓扑结构上使增强子与启动子分离。这种经过合理设计的、可诱导的类似绝缘子的元件重现了在体内观察到的真核生物绝缘子的许多关键特性。这些数据提示了增强子和绝缘子作用的新机制。
