G-quadruplex DNA as a target for pathogenic bacteria: efficacy of an extended naphthalene diimide ligand and mode of action. G-quadruplex DNA as a target for pathogenic bacteria: efficacy of an extended naphthalene diimide ligand and mode of action

Guanidine DNA quadruplex (G4-DNA) structures convey a distinctive layer of epigenetic information that is critical for the regulation of key biological activities and processes as genome transcription regulation, replication and repair. Despite several works that have been published recently, the information regarding their role and possible use as therapeutic drug targets in bacteria is still scarce. Here, we tested the biological activity of a small G4-DNA ligand library based on the naphthalene diimide (NDI) pharmacophore, against both Gram-positive and Gram-negative bacteria. For the best compound identified, NDI-10, the action mechanism was further characterized. Gram-negative bacteria were more resistant altogether due to the presence of the outer membrane, although the activity of the G4-Ligand was generally bactericidal, while it was bacteriostatic for Gram-positive bacteria. This asymmetric activity could be related to the different prevalence of putative G4-DNA structures in each group, the influence that they can exert on the gene expression (which was found more severe for the Gram-negative bacteria) and the role of the G4 structures in these bacteria, that seems to be more related to promote transcription in Gram-positive bacteria and repress transcription in Gram-negative. Overall design: 4 samples Ecoli and 4 samples Saureus no replicates

胍基DNA四链体（Guanidine DNA quadruplex, G4-DNA）结构承载着一类独特的表观遗传信息层，对于诸如基因组转录调控、复制与修复等关键生物学活动与过程的调控至关重要。尽管近期已有多项相关研究发表，但关于其在细菌中的功能及作为治疗性药物靶点的潜在应用的相关信息仍较为匮乏。本研究针对基于萘二酰亚胺（naphthalene diimide, NDI）药效团构建的小型G4-DNA配体库，开展了针对革兰氏阳性菌与革兰氏阴性菌的生物学活性测试。针对筛选得到的最优化合物NDI-10，本研究进一步阐明了其作用机制。尽管G4配体的活性总体上呈现杀菌作用，但由于革兰氏阴性菌具有外膜结构，其整体对该配体的耐药性更强，而该配体对革兰氏阳性菌则仅表现为抑菌作用。这种不对称活性可能与两类细菌中推定G4-DNA结构的不同分布频率、其对基因表达的调控作用（其中革兰氏阴性菌受影响更为显著）以及G4结构在两类细菌中的功能差异相关：在革兰氏阳性菌中，G4结构主要促进转录，而在革兰氏阴性菌中则主要抑制转录。实验整体设计：共设置4份大肠杆菌（Escherichia coli, E. coli）样本与4份金黄色葡萄球菌（Staphylococcus aureus, S. aureus）样本，未设置生物学重复。