Single-molecule probing the duplex and G4 unwinding patterns of a RecD family helicase
Single-molecule probing the duplex and G4 unwinding patterns of a RecD family helicase
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单分子探测 RecD 家族解旋酶的双链体和 G4 解旋模式
DOI：
10.1016/j.ijbiomac.2020.07.158
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发表时间：
2020
影响因子：
8.2
通讯作者：
Li-Jun Guo
中科院分区：
文献类型：
--
作者：
Zhen-Yong Xue;Wen-Qiang Wu;Xiao-Cong Zhao;Arvind Kumar;Xia Ran;Xing-Hua Zhang;Yu Zhang;Li-Jun Guo
RecD家族解旋酶在原核生物基因组稳定性中发挥重要作用，是研究超家族1B （SF1B）解旋酶的结构模型。然而，recd催化的双链DNA解绕行为及其潜在机制仍然是难以捉摸的。RecD家族解旋酶与真核生物Pif1家族解旋酶具有共同的原解旋酶，Pif1家族解旋酶以其出色的g -四重体（G4）解绕能力而闻名。然而，关于RecD解旋酶是否以及如何展开G4结构仍然存在争议。本文利用单分子荧光共振能量转移（smFRET）和磁镊子（MT）研究了耐辐射球菌（deinococcus radioduransRecD2）介导的双链DNA解绕和G4结构的解析。在双链DNA上观察到一种对称的、重复的解绕现象，这是由一个单体的链开关和易位揭示的。此外，我们发现DrRecD2能够展开平行和反平行的G4结构，没有明显的拓扑偏好。令人惊讶的是，RecD在双链和G4 DNA上的解绕特性与Pif1不同。这一发现为SF1B解旋酶的解绕机制和功能的理解提供了一个例子，说明来自同一个祖先的两个分子在进化过程中模式发生了偏离。
RecD family helicases play an important role in prokaryotic genome stability and serve as the structural models for studying superfamily 1B (SF1B) helicases. However, RecD-catalyzed duplex DNA unwinding behavior and the underlying mechanism are still elusive. RecD family helicases share a common proto-helicase with eukaryotic Pif1 family helicases, which are well known for their outstanding G-quadruplex (G4) unwinding ability. However, there are still controversial points as to whether and how RecD helicases unfold G4 structures. Here, single-molecule fluorescence resonance energy transfer (smFRET) and magnetic tweezers (MT) were used to studyDeinococcus radioduransRecD2 (DrRecD2)-mediated duplex DNA unwinding and resolution of G4 structures. A symmetric, repetitive unwinding phenomenon was observed on duplex DNA, revealed from the strand switch and translocation of one monomer. Furthermore, we found that DrRecD2 was able to unwind both parallel and antiparallel G4 structures without obvious topological preferences. Surprisingly, the unwinding properties of RecD on duplex and G4 DNA are different from those of Pif1. The findings provide an example, in which the patterns of two molecules derived from a common ancestor deviate during evolution, and they are of significance for understanding the unwinding mechanism and function of SF1B helicases.