RNA and DNA G-quadruplexes bind to human Dicer and inhibit its activity;

Guanine (G)-rich single-stranded nucleic acids can adopt G-quadruplex structures. Accumulating evidence indicates that G-quadruplexes serve important regulatory roles in fundamental biological processes such as DNA replication, transcription, and translation, while aberrant G-quadruplex formation is linked to genome instability and cancer. Understanding the biological functions played by G-quadruplexes requires detailed knowledge of their protein interactome. Here, we report that both RNA and DNA G-quadruplexes are bound by human Dicer in vitro. Using in vitro binding assays, mutation studies, and computational modeling we demonstrate that G-quadruplexes can interact with the Platform-PAZ-Connector helix cassette of Dicer, the region responsible for anchoring microRNA precursors (pre-miRNAs). Consequently, we show that G-quadruplexes efficiently and stably inhibit the cleavage of pre-miRNA by Dicer. Our data highlight the potential of human Dicer for binding of G-quadruplexes and allow us to propose a G-quadruplex-driven sequestration mechanism of Dicer regulation.富含鸟嘌呤（G）的单链核酸可形成G-四链体（G-quadruplex）结构。越来越多的研究证据表明，G-四链体在DNA复制、转录及翻译等核心生物学过程中发挥关键调控作用，而异常形成的G-四链体与基因组不稳定及癌症发生密切相关。解析G-四链体的生物学功能，需要深入掌握其蛋白质互作组的相关信息。本研究证实，在体外环境中，人源Dicer可同时结合RNA与DNA来源的G-四链体。通过体外结合实验、突变研究与计算建模，我们证明G-四链体可与Dicer的Platform-PAZ-Connector螺旋盒区域结合，该区域正是锚定微RNA前体（pre-miRNA）的关键结构域。进一步实验结果显示，G-四链体能够高效且稳定地抑制Dicer对pre-miRNA的切割活性。本研究揭示了人源Dicer结合G-四链体的潜在能力，并据此提出了一种由G-四链体介导的Dicer调控隔离机制。