靶向核酸i-motif结构的荧光探针的设计、合成及应用研究

I-motif是连续富胞嘧啶序列所形成的核酸特殊二级结构，广泛存在于癌基因启动子区和端粒末端，是癌基因转录调控和维持端粒长度的分子开关和潜在抗癌靶标。靶向i-motif形成或解链的探针分子可以对i-motif实现精准检测和示踪，对其结构与功能关系的研究起关键作用。我们前期研究发现i-motif配体吖啶酮—荧光团融合物NP-ADO-1能特异性作用于i-motif，并使相应荧光信号显著增强，而对G-四链体和双链DNA没有明显作用。本项目将在此基础上，将吖啶酮衍生物和多种荧光团进行融合，建立靶向i-motif荧光探针库，筛选出性能更优异的i-motif荧光探针，实现对i-motif结构的精准检测，研究探针分子与i-motif结构的作用模式和规律，探讨细胞内i-motif的行为和动态变化过程。本研究为阐明i-motif在复杂生物体系中参与生命调控网络的作用和意义，以及相关靶向药物研究提供有力依据。

I-motifs are special secondary structures of nucleic acids formed by consequent cytosine-rich sequences, existing extensively in the promoter region and telomeric region of oncogene, which can act as molecular switches for oncogene transcriptional regulation and maintenance of telomere length, and therefore, i-motif structures are potential antitumor drug targets. Molecular probes targeting formation or unfolding of i-motifs can be used for accurate detection and tracking of i-motifs, which play key roles in the research for i-motif structures and functions in cells. In our preliminary study, we found that compound NP-ADO-1 with combination of i-motif binding ligand acridone and a fluorophore could interact with i-motif selectively, resulting in remarkable enhancement of fluorescence signals, without significant interaction to G-quadruplex and double-stranded DNA. On the base of these important findings, we plan to compromise acridone derivatives with multiple fluorophores, and further optimize the structures to construct a fluorescent probe library targeting i-motifs, for screening better i-motif specific fluorescent probes to achieve accurate detection. We also plan to study the action mode and mechanism for the binding of fluorescent probes to i-motifs, to explore the behavior and dynamics of i-motifs in cells. This project might provide a useful theoretical and experimental basis for further exploring and verifying function and significance of i-motifs in regulation network in complex biological systems, as well as discovery of new types of targeted drugs.