Genomics
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At their ends, telomeres can assume special structures, the G quartets. G quartets can account for the stability properties of chromosome ends. The formation of intermolecular G quartets can account for the apparent interaction of telomeres (bouqet formation).()
Guanine-rich DNA and RNA have the ability to form inter- and intramolecular four-stranded structures, referred to as G-quartets (, ).
G-quartets arise from the association of four G-bases into a cyclic Hoogsteen H-bonding arrangement, and each G-base makes two H-bonds with its neighbor G-base (N1 to O6 and N2 to N7). G-quartets stack on top of each other to give rise to tetrad-helical structures. The stability of G-quartet structures depends on several factors: the presence of the monovalent cations, the concentration of the G-rich oligonucleotides present, and the sequence of the G-rich oligonucleotides under study. Potassium with the optimal size to interact within a G-octamer greatly promotes the formation of G-quartet structures and increases their stability. G-quartet oligodeoxynucleotides (GQ-ODNs) have been suggested to play a critical role in several biological processes including modulation of telomere activity () , inhibition of human thrombin () , HIV infection (, ) , HIV-1 integrase activity (1, 2, 3) , human nuclear topoisomerase 1 activity () , and DNA replication in vitro () .
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