Nelson P
Department of Physics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Proc Natl Acad Sci U S A. 1999 Dec 7;96(25):14342-7. doi: 10.1073/pnas.96.25.14342.
It is well known that transcription can induce torsional stress in DNA, affecting the activity of nearby genes or even inducing structural transitions in the DNA duplex. It has long been assumed that the generation of significant torsional stress requires the DNA to be anchored, forming a limited topological domain, because otherwise it would spin almost freely about its axis. Previous estimates of the rotational drag have, however, neglected the role of small natural bends in the helix backbone. We show how these bends can increase the drag several thousandfold relative to prior estimates, allowing significant torsional stress even in linear unanchored DNA. The model helps explain several puzzling experimental results on structural transitions induced by transcription of DNA.
众所周知,转录可在DNA中诱导扭转应力,影响附近基因的活性,甚至诱导DNA双链体发生结构转变。长期以来,人们一直认为,产生显著的扭转应力需要DNA被锚定,形成一个有限的拓扑结构域,因为否则它会几乎围绕其轴自由旋转。然而,先前对旋转阻力的估计忽略了螺旋骨架中小的自然弯曲的作用。我们展示了这些弯曲如何能使阻力相对于先前的估计增加数千倍,即使在没有锚定的线性DNA中也能产生显著的扭转应力。该模型有助于解释一些关于DNA转录诱导结构转变的令人困惑的实验结果。