Gao Bo, Zheng Ya-Ting, Su Ai-Min, Sun Bo, Xi Xu-Guang, Hou Xi-Miao
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling 712100, China.
School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.
iScience. 2021 Dec 6;25(1):103575. doi: 10.1016/j.isci.2021.103575. eCollection 2022 Jan 21.
I-motifs are noncanonical four-stranded DNA structures formed by C-rich sequences at acidic environment with critical biofunctions. The particular pH sensitivity has inspired the development of i-motifs as pH sensors and DNA motors in nanotechnology. However, the folding and regulation mechanisms of i-motifs remain elusive. Here, using single-molecule FRET, we first show that i-motifs are more dynamic than G4s. Impressively, i-motifs display a high diversity of six folding species with slow interconversion. Further results indicate that i-motifs can be linearized by Replication protein A. More importantly, we identified a number of helicases with high specificity to i-motifs at low pH. All these helicases directly act on and efficiently resolve i-motifs into intermediates independent of ATP, although they poorly unwind G4 or duplex at low pH. Owing to the extreme sensitivity to helicases and no need for ATP, i-motif may be applied as a probe for helicase sensing both and .
i-基序是由富含C的序列在酸性环境中形成的具有关键生物功能的非经典四链DNA结构。其独特的pH敏感性激发了i-基序在纳米技术中作为pH传感器和DNA马达的发展。然而，i-基序的折叠和调控机制仍然不清楚。在这里，我们使用单分子荧光共振能量转移技术，首次表明i-基序比G4更具动态性。令人印象深刻的是，i-基序展示出六种折叠形式的高度多样性，且相互转换缓慢。进一步的结果表明，复制蛋白A可以使i-基序线性化。更重要的是，我们鉴定出了一些在低pH下对i-基序具有高特异性的解旋酶。所有这些解旋酶直接作用于i-基序，并在不依赖ATP的情况下有效地将其解析为中间体，尽管它们在低pH下很难解开G4或双链体。由于对解旋酶极度敏感且无需ATP，i-基序可能作为一种用于检测解旋酶的探针。
