Department of Biochemistry and Molecular Pharmacology, Instituto de Parasitología y Biomedicina, CSIC , PTS Granada, Avda. del Conocimiento, 17, 18016 Armilla, Granada, Spain.
ARNA Laboratory, Université de Bordeaux, Inserm U1212, CNRS UMR5320, Institut Européen de Chimie Biologie (IECB), 2 Rue Robert Escarpit, 33607 Pessac, France.
J Med Chem. 2018 Feb 8;61(3):1231-1240. doi: 10.1021/acs.jmedchem.7b01672. Epub 2018 Jan 27.
G-quadruplexes (G4) are DNA secondary structures that take part in the regulation of gene expression. Putative G4 forming sequences (PQS) have been reported in mammals, yeast, bacteria, and viruses. Here, we present PQS searches on the genomes of T. brucei, L. major, and P. falciparum. We found telomeric sequences and new PQS motifs. Biophysical experiments showed that EBR1, a 29 nucleotide long highly repeated PQS in T. brucei, forms a stable G4 structure. G4 ligands based on carbohydrate conjugated naphthalene diimides (carb-NDIs) that bind G4's including hTel could bind EBR1 with selectivity versus dsDNA. These ligands showed important antiparasitic activity. IC values were in the nanomolar range against T. brucei with high selectivity against MRC-5 human cells. Confocal microscopy confirmed these ligands localize in the nucleus and kinetoplast of T. brucei suggesting they can reach their potential G4 targets. Cytotoxicity and zebrafish toxicity studies revealed sugar conjugation reduces intrinsic toxicity of NDIs.
四链体（G4）是参与基因表达调控的 DNA 二级结构。在哺乳动物、酵母、细菌和病毒中都报道了推定的四链体形成序列（PQS）。在这里，我们对 T. brucei、L. major 和 P. falciparum 的基因组进行了 PQS 搜索。我们发现了端粒序列和新的 PQS 基序。生物物理实验表明，EBR1 是 T. brucei 中一个 29 个核苷酸长的高度重复的 PQS，形成了一个稳定的 G4 结构。基于糖共轭萘二酰亚胺（carb-NDI）的 G4 配体可以结合包括 hTel 在内的 G4，对 EBR1 具有选择性，而对 dsDNA 没有选择性。这些配体表现出重要的抗寄生虫活性。对 T. brucei 的 IC 值在纳摩尔范围内，对 MRC-5 人细胞具有高选择性。共聚焦显微镜证实这些配体定位于 T. brucei 的核和动基体，表明它们可以到达其潜在的 G4 靶标。细胞毒性和斑马鱼毒性研究表明，糖缀合降低了 NDI 的内在毒性。
