Lyubchenko Y L, Shlyakhtenko L S, Aki T, Adhya S
Department of Microbiology, Arizona State University, Tempe 85287-2701, USA.
Nucleic Acids Res. 1997 Feb 15;25(4):873-6. doi: 10.1093/nar/25.4.873.
Regulation of gene transcription in both prokaryotes and eukaryotes involves formation of various DNA-multiprotein complexes of higher order structure through communication between distant regions of DNA. The communication between distant DNA sites occurs by interaction between proteins bound to the sites by looping out the intervening DNA segments. The repression of transcription of two overlapping promoters of the gal operon in Escherichia coli requires Gal repressor (GalR) and the histone-like protein HU. Both in vivo and in vitro data support a proposed HU containing complex responsive to induction in which GalR molecules bound to two distant operator sites interact by looping out DNA. We successfully applied atomic force microscope (AFM) imaging to visualize galDNA complexes with proteins. We report GalR mediated DNA looping in which HU plays an obligatory role by helping GalR tetramerization. Supercoiling of DNA, which is also critical for GalR action, may stabilize the DNA loops by providing an energetically favorable geometry of the DNA.
原核生物和真核生物中的基因转录调控都涉及通过DNA远距离区域之间的通讯形成各种具有更高阶结构的DNA-多蛋白复合物。远距离DNA位点之间的通讯是通过结合到这些位点的蛋白质之间的相互作用发生的，其间的DNA片段会形成环。大肠杆菌中半乳糖操纵子两个重叠启动子的转录抑制需要半乳糖阻遏物（GalR）和类组蛋白HU。体内和体外数据均支持一种拟议的含有HU的复合物对诱导有反应，其中结合到两个远距离操纵位点的GalR分子通过使DNA成环而相互作用。我们成功应用原子力显微镜（AFM）成像来可视化与蛋白质结合的半乳糖操纵子DNA复合物。我们报告了GalR介导的DNA成环，其中HU通过帮助GalR四聚化发挥必不可少的作用。对GalR作用也至关重要的DNA超螺旋，可能通过提供能量上有利的DNA几何形状来稳定DNA环。
