Nucleic Acids Research Laboratory, Department of Chemistry, University of Delhi (North Campus), Delhi, India.
Department of Chemistry, Ramjas College, University of Delhi, Delhi, India.
J Mol Recognit. 2022 Mar;35(3):e2950. doi: 10.1002/jmr.2950. Epub 2022 Jan 6.
Porphyrins are among the first ligands that have been tested for their quadruplex binding and stabilization potential. We report the differential interaction of the positional cationic porphyrin isomers TMPyP3 and TMPyP4 with a parallel G-quadruplex (GQ) formed by 33-mer (TP) regulatory sequence present in the promoter region of the human multidrug resistance protein 1 (MRP1) transporter gene. This GQ element encompasses the three evolutionary conserved SP1 transcription factor binding sites. Taking into account that SP1 binds to a non-canonical GQ motif with higher affinity than to a canonical duplex DNA consensus motif, it is suggestive that GQ distortion by cationic porphyrin will have important implications in the regulation of MRP1 expression. Herein, we employed biophysical analysis using circular dichroism, visible absorption, UV-thermal melting and steady-state fluorescence spectroscopy, reporting destabilization of MRP1 GQ by cationic porphyrins. Results suggest that TMPyP4 and TMPyP3 interact with GQ with a binding affinity of 10 to 10 M . Thermodynamic analysis indicated a significant decrease in melting temperature of GQ (ΔTm of 15.5°C-23.5°C), in the presence of 2 times excess of porphyrins. This study provides the biophysical evidence indicating the destabilisation of a parallel DNA G-quadruplex by cationic porphyrins.
卟啉类化合物是最早被测试其四链体结合和稳定潜力的配体之一。我们报告了位置阳离子卟啉异构体 TMPyP3 和 TMPyP4 与平行 G-四链体（GQ）的差异相互作用，该 GQ 由人类多药耐药蛋白 1（MRP1）转运基因启动子区域中存在的 33 个核苷酸（TP）调节序列形成。该 GQ 元件包含三个进化保守的 SP1 转录因子结合位点。考虑到 SP1 与非典型 GQ 基序的结合亲和力高于与典型双链 DNA 共识基序的结合亲和力，因此阳离子卟啉对 GQ 的扭曲将对 MRP1 表达的调控具有重要意义。在此，我们使用圆二色性、可见吸收、紫外-热融解和稳态荧光光谱等生物物理分析方法，报告了阳离子卟啉对 MRP1 GQ 的失稳作用。结果表明，TMPyP4 和 TMPyP3 与 GQ 的结合亲和力为 10 到 10 M 。热力学分析表明，在卟啉过量 2 倍的情况下，GQ 的熔点显著降低（ΔTm 为 15.5°C-23.5°C）。这项研究提供了生物物理证据，表明阳离子卟啉使平行 DNA G-四链体失稳。
