quadruplexes

Quadruplexes, also known as G-quadruplexes or G4 structures, are four-stranded nucleic acid structures. They are formed in guanine-rich sequences of DNA or RNA. The formation of these structures relies on the Hoogsteen hydrogen bonding between guanine bases, leading to the creation of a planar guanine quartet. These quartets can then stack on top of each other, forming a stable G-quadruplex core. The specific arrangement of these quartets and the intervening loops can vary, leading to different topologies of quadruplexes.

These non-canonical structures are found in various regions of the genome, including telomeres, promoter regions of oncogenes, and ribosomal DNA. Their presence is not merely a structural curiosity; G-quadruplexes play significant roles in regulating gene expression, DNA replication, and telomere maintenance. They can act as roadblocks for DNA polymerases, influence transcription factor binding, and are recognized by specific proteins that interact with them.

The study of quadruplexes has gained considerable attention due to their potential as therapeutic targets. The ability of G-quadruplexes to form in biologically relevant regions, particularly in cancer-associated genes, makes them attractive targets for small molecule drugs. Compounds that stabilize or destabilize G-quadruplex structures are being investigated for their potential in cancer treatment and other diseases. Understanding the dynamics and biological functions of these unique nucleic acid structures remains an active area of research.