G-quadruplex

A nucleic-acid structure formed by stacked guanine quartets stabilized by monovalent cations. It can arise in guanine-rich DNA or RNA sequences and adopt diverse topologies.

G-quartet: A planar arrangement of four guanine bases joined by Hoogsteen hydrogen bonds. Stacked quartets form the structural core of a G-quadruplex.
Guanine: A purine nucleobase found in DNA and RNA that pairs canonically with cytosine. Its hydrogen-bonding edges allow four guanines to assemble into a quartet.
Telomere: A repetitive DNA-protein structure that protects the ends of linear chromosomes. Guanine-rich telomeric DNA can fold into G-quadruplexes.
B-DNA: The common right-handed double-helical form of DNA under physiological conditions. G-quadruplexes provide a noncanonical alternative structure within some DNA regions.
G-quadruplex in vivo: A G-quadruplex structure that forms or persists inside a living cell. Its abundance and lifetime in cells remain difficult to establish directly.
Hoogsteen base pair: A noncanonical nucleic-acid base pair formed through Hoogsteen-edge hydrogen bonding. Hoogsteen bonds connect guanines within each quartet.
DNA: A nucleic acid that stores hereditary information in most organisms. G-quadruplexes can form within guanine-rich regions of genomic DNA.
Promoter: A DNA region where transcription machinery assembles to initiate gene transcription. G-quadruplex-forming sequences in promoters can influence transcription.
i-motif: A four-stranded DNA structure formed by intercalated, protonated cytosine pairs. It is a distinct noncanonical DNA structure associated with cytosine-rich sequences.
G-quadruplex helicase: A helicase capable of unwinding or resolving G-quadruplex structures. Cellular helicases can regulate how long quadruplexes persist in DNA or RNA.

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