School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy.
Department of Comparative Biomedicine and Food Science, University of Padova, 35020 Legnaro (PD), Italy.
Nucleic Acids Res. 2021 May 7;49(8):4564-4573. doi: 10.1093/nar/gkab079.
G-quadruplexes (G4s) are tetrahelical DNA structures stabilized by four guanines paired via Hoogsteen hydrogen bonds into quartets. While their presence within eukaryotic DNA is known to play a key role in regulatory processes, their functional mechanisms are still under investigation. In the present work, we analysed the nanomechanical properties of three G4s present within the promoter of the KIT proto-oncogene from a single-molecule point of view through the use of magnetic tweezers (MTs). The study of DNA extension fluctuations under negative supercoiling allowed us to identify a characteristic fingerprint of G4 folding. We further analysed the energetic contribution of G4 to the double-strand denaturation process in the presence of negative supercoiling, and we observed a reduction in the energy required for strands separation.
四链体（G4s）是由四个通过 Hoogsteen 氢键配对形成四联体的鸟嘌呤稳定的四螺旋 DNA 结构。虽然它们在真核生物 DNA 中的存在被认为在调节过程中起着关键作用，但它们的功能机制仍在研究中。在本工作中，我们通过使用磁镊（MTs）从单分子角度分析了 KIT 原癌基因启动子中存在的三个 G4 的纳米力学特性。在负超螺旋存在下研究 DNA 延伸波动，使我们能够识别 G4 折叠的特征指纹。我们进一步分析了负超螺旋存在时 G4 对双链变性过程的能量贡献，我们观察到链分离所需的能量减少。
