Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization , University of Maryland , College Park , Maryland 20742 , United States.
J Am Chem Soc. 2018 Nov 28;140(47):16291-16298. doi: 10.1021/jacs.8b10153. Epub 2018 Nov 13.
DNA can adopt many structures beyond the Watson-Crick duplex. However, the bounds of DNA structural diversity and how these structures might regulate biological processes is only beginning to be understood. Here, we describe the 1.05 Å resolution crystal structure of a DNA oligonucleotide that self-associates to form a non-G-quadruplex fold-back structure. Distinct from previously described fold-back quadruplexes, two-fold-back dimers interact through noncanonical and Watson-Crick interactions to form a tetrameric assembly. These interactions include a hexad base pairing arrangement from two C-G-G base triples. The assembly is dependent on divalent cations, and the interface between the dimeric units creates a cavity in which a cation resides. This structure provides new sequence and structural contexts for the formation of fold-back quadruplexes, further highlighting the potential biological importance of this type of noncanonical DNA structure. This structure may also serve as the basis for designing new types of DNA nanoarchitectures or cation sensors based on the strong divalent cation dependence.
DNA 可以采用超越沃森-克里克双链体的多种结构。然而，DNA 结构多样性的范围以及这些结构如何调节生物过程才刚刚开始被理解。在这里，我们描述了一个 DNA 寡核苷酸的 1.05Å分辨率晶体结构，该寡核苷酸自身缔合形成非 G-四联体折叠回结构。与以前描述的折叠回四联体不同，两个折叠回二聚体通过非规范和沃森-克里克相互作用相互作用形成四聚体组装。这些相互作用包括来自两个 C-G-G 碱基三对的六碱基配对排列。组装依赖于二价阳离子，并且二聚体单元之间的界面在其中容纳一个阳离子。该结构为折叠回四联体的形成提供了新的序列和结构背景，进一步强调了这种类型的非规范 DNA 结构的潜在生物学重要性。该结构还可以作为基于强二价阳离子依赖性设计新型 DNA 纳米结构或阳离子传感器的基础。
