RNA G-quadruplexes: emerging regulators of gene expression and therapeutic targets.

RNA G-quadruplexes (rG4s) are non-canonical, four-stranded secondary structures formed by guanine-rich RNA sequences. These dynamic elements have garnered significant attention for their critical roles in regulating gene expression, including translation, alternative splicing, mRNA localization, and stability. This review synthesizes recent progress in understanding the structural determinants and formation dynamics of rG4s, highlighting the contributions of sequence motifs, ionic conditions, and RNA-binding proteins to their stability and function. Functional studies reveal that rG4s modulate key oncogenic transcripts (e.g., MYC, BCL2), contribute to splicing regulation, and influence intracellular RNA trafficking. In pathological contexts, rG4s have been implicated in the molecular etiology of cancers, neurodegenerative diseases such as amyotrophic lateral sclerosis and Fragile X syndrome, and viral replication mechanisms in pathogens including HIV and SARS-CoV-2. Advances in high-throughput techniques, such as G4-seq, rG4-seq, and live-cell imaging, have facilitated the global identification and characterization of rG4s in physiological and disease settings. Moreover, the therapeutic targeting of rG4s using small molecules holds promise for selective gene regulation and biomarker development. Comparative analyses across in vitro, in vivo, and clinical studies underscore the cell-type-specific and context-dependent roles of rG4s, especially in mediating stress responses and apoptosis. Despite methodological limitations and challenges in achieving targeted delivery, rG4s represent a compelling frontier for precision medicine. This review outlines current insights and future directions toward harnessing rG4 biology for therapeutic innovation.