Department of Physics, Kyoto University, Kyoto, Japan.
Biophys J. 2013 Aug 20;105(4):1037-44. doi: 10.1016/j.bpj.2013.07.025.
The effects of nucleoid proteins Fis and Dps of Escherichia coli on the higher order structure of a giant DNA were studied, in which Fis and Dps are known to be expressed mainly in the exponential growth phase and stationary phase, respectively. Fis causes loose shrinking of the higher order structure of a genome-sized DNA, T4 DNA (166 kbp), in a cooperative manner, that is, the DNA conformational transition proceeds through the appearance of a bimodal size distribution or the coexistence of elongated coil and shrunken globular states. The effective volume of the loosely shrunken state induced by Fis is 30-60 times larger than that of the compact state induced by spermidine, suggesting that cellular enzymes can access for DNA with the shrunken state but cannot for the compact state. Interestingly, Dps tends to inhibit the Fis-induced shrinkage of DNA, but promotes DNA compaction in the presence of spermidine. These characteristic effects of nucleotide proteins on a giant DNA are discussed by adopting a simple theoretical model with a mean-field approximation.
研究了大肠杆菌的核蛋白 Fis 和 Dps 对巨大多形性 DNA 高级结构的影响，已知 Fis 和 Dps 主要在指数生长阶段和静止阶段表达。Fis 以协同方式导致基因组大小的 T4 DNA（166 kbp）高级结构松散收缩，即 DNA 构象转变通过出现双峰大小分布或伸长线圈和收缩球状状态共存来进行。由 Fis 诱导的松散收缩状态的有效体积比由 spermidine 诱导的紧密状态大 30-60 倍，这表明细胞酶可以访问具有收缩状态的 DNA，但不能访问紧密状态的 DNA。有趣的是，Dps 倾向于抑制 Fis 诱导的 DNA 收缩，但在 spermidine 存在下促进 DNA 压缩。通过采用具有平均场近似的简单理论模型，讨论了核苷酸蛋白对巨大多形性 DNA 的这些特征影响。
