相互分离且距离较远的DNA区域能够相互作用是通过一种特异蛋白诱导的突触蛋白-DNA复合体作为媒介的。这种现象普遍存在，在基因工程中的地位也至关重要。虽然这种相互作用通常发生在两点之间，而现在已经发现三个特定DNA 区域也能够相互作用，并且已经有相应的模式。
用原子力显微镜观测这种模式为EcoRII的限制性内切酶，可以显示和表征涉及到三个DNA结合点的突触蛋白-DNA复合体。该复合体用图像显示出来是双环结构，通过环上的长度测量可以证明特异性蛋白在复合体中所处的位置。蛋白质的体积测量显示，EcoRII二聚体是三点突触体的核心。蛋白质的体积数据显示，该二聚体形式的蛋白质也是形成其它类型突触复合体的原因。
目前，研究人员正在探讨应用上述结果去认识蛋白质-DNA反应的机制。
英文原文链接：http://pubs.acs.org/cgi-bin/abstract.cgi/bichaw/2007/46/i39/abs/bi701123u.html
Biochemistry, 46 (39), 11128 -11136, 2007. 10.1021/bi701123u S0006-2960(70)01123-6
Web Release Date: September 11, 2007 Copyright © 2007 American Chemical Society
Direct Visualization of the EcoRII-DNA Triple Synaptic Complex by Atomic Force Microscopy
Luda S. Shlyakhtenko, Jamie Gilmore, Alex Portillo, Gintautas Tamulaitis, Virginijus Siksnys, and Yuri L. Lyubchenko*
Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, and Institute of Biotechnology, Graiciuno 8, LT-02241 Vilnius, Lithuania
Received June 6, 2007
Revised Manuscript Received August 20, 2007
Abstract
Interactions between distantly separated DNA regions mediated by specialized proteins lead to the formation of synaptic protein-DNA complexes. This is a ubiquitous phenomenon which is critical in various genetic processes. Although such interactions typically occur between two sites, interactions among three specific DNA regions have been identified, and a corresponding model has been proposed. Atomic force microscopy was used to test this model for the EcoRII restriction enzyme and provide direct visualization and characterization of synaptic protein-DNA complexes involving three DNA binding sites. The complex appeared in the images as a two-loop structure, and the length measurements proved the site specificity of the protein in the complex. The protein volume measurements showed that an EcoRII dimer is the core of the three-site synaptosome. Other complexes were identified and analyzed. The protein volume data showed that the dimeric form of the protein is responsible for the formation of other types of synaptic complexes as well. The applications of these results to the mechanisms of the protein-DNA interactions are discussed
