Son Heyjin, Bae Sangsu, Lee Sanghwa
Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.
Department of Chemistry, Hanyang University, Seoul, 04763, Republic of Korea.
Biochem Biophys Res Commun. 2021 Oct 30;583:142-145. doi: 10.1016/j.bbrc.2021.10.065.
Z-DNA has attracted interest due to its distinctive left-handed helical structure. This non-canonical DNA structure is able to form transiently and plays an important role in cellular processes such as transcriptional regulation and DNA recombination. Alternating purine-pyrimidine sequences are well known to form Z-DNA under high-salt conditions, but the detailed mechanism of B-to-Z transition of DNA containing BZ junctions under these conditions is not well understood. Here, using single-molecule FRET and circular dichroism experiments, we studied the effect of BZ junctions on Z-DNA formation under high-salt conditions. Further thermodynamic analysis revealed that a discrepancy of different DNA substrates in the presence and absence of BZ junctions in Z-DNA formation can be attributed mainly to the competition between enthalpy and entropy. Salt-induced B-to-Z transition is entropically favored in the presence of BZ junctions and is enthalpically favored in their absence. This thermodynamic information provides a deeper understanding of Z-DNA formation of DNA containing BZ junctions.
Z-DNA因其独特的左手螺旋结构而备受关注。这种非典型的DNA结构能够瞬时形成，并在转录调控和DNA重组等细胞过程中发挥重要作用。众所周知，交替的嘌呤-嘧啶序列在高盐条件下会形成Z-DNA，但在这些条件下含有BZ连接的DNA从B型向Z型转变的详细机制尚不清楚。在这里，我们使用单分子荧光共振能量转移和圆二色性实验，研究了BZ连接在高盐条件下对Z-DNA形成的影响。进一步的热力学分析表明，在Z-DNA形成过程中，存在和不存在BZ连接时不同DNA底物的差异主要可归因于焓和熵之间的竞争。在存在BZ连接的情况下，盐诱导的B型向Z型转变在熵方面是有利的，而在不存在BZ连接的情况下则在焓方面是有利的。这些热力学信息为深入理解含有BZ连接的DNA的Z-DNA形成提供了依据。
