Beijing National Laboratory for Condensed Matter Physics and Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Phys Rev Lett. 2012 Nov 21;109(21):218102. doi: 10.1103/PhysRevLett.109.218102. Epub 2012 Nov 20.
DNA wrapping is an important mechanism for chromosomal DNA packaging in cells and viruses. Previous studies of DNA wrapping have been performed mostly on torsionally unconstrained DNA, while in vivo DNA is often under torsional constraint. In this study, we extend a previously proposed theoretical model for wrapping of torsionally unconstrained DNA to a new model including the contribution of DNA twist energy, which influences DNA wrapping drastically. In particular, due to accumulation of twist energy during DNA wrapping, it predicts a finite amount of DNA that can be wrapped on a helical spool. The predictions of the new model are tested by single-molecule study of DNA wrapping under torsional constraint using magnetic tweezers. The theoretical predictions and the experimental results are consistent with each other and their implications are discussed.
DNA 包装是细胞和病毒中染色体 DNA 包装的重要机制。以前对 DNA 包装的研究主要是在没有扭转约束的 DNA 上进行的，而体内的 DNA 通常受到扭转约束。在这项研究中，我们将以前提出的用于包装无扭转约束 DNA 的理论模型扩展到一个新的模型，该模型包括影响 DNA 包装的扭转能的贡献。特别是，由于在 DNA 包装过程中扭转能的积累，它预测了可以缠绕在螺旋轴上的有限量的 DNA。新模型的预测通过使用磁镊在扭转约束下对 DNA 包装的单分子研究进行了测试。理论预测与实验结果相互一致，并讨论了它们的意义。
