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G Quartet oligonucleotides
See AlsoDescription
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).( {{http://opbs.okstate.edu/~Melcher/MG/MGw1/MG1352.html}} )
Guanine-rich DNA and RNA have the ability to form inter- and intramolecular four-stranded structures, referred to as G-quartets ( {{Williamson JR. G-quartet structures in telomeric DNA. Annu Rev Biophys Biomol Structure, 1994;23:703-30}} , {{Gilber DE, Feigon J. Multistranded DNA structures. Current Opinion Structura Biol, 1999;9:305-14}} ).
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 ( {{Sen D, Gilbert W. Formation of parallel four-stranded complexes by guanine-rich motif for meiosis. Nature, 1998;334:364-6}} ) , inhibition of human thrombin ( {{Bock LC, Griffin LC, Latham JA, Vermaas EH, Toole JJ. Selection of single-stranded DNA molecules that bind and inhibit human thrombin. Nature, 1992;355:564-6,}} ) , HIV infection ( {{Wyatt JR, Vickers TA, Roberson JL, et al Combinatorially selected guanosine-quartet structure is a potent inhibitor of HIV envelope-mediated cell fusion. Proc Natl Acad Sci USA, 1994;91:1356-60}} , {{Mazumder A, Neamati N, Ojwang JO, Sunder S, Rando RF, Pommier Y. Inhibition of the human immunodeficiency virus type 1 integrase by guanosine quartet structures. Biochemistry, 1996;35:13762-71}} ) , HIV-1 integrase activity (1, 2, 3) , human nuclear topoisomerase 1 activity ( {{Rando RF, Ojwang J, Elbaggari A, et al Suppression of human immunodeficiency virus type 1 activity in vitro by oligonucleotides which form intramolecular tetrads. J Biol Chem, 1995;270:1754-60}} ) , and DNA replication in vitro ( {{Xu X, Hamhouyia F, Thomas SD, et al Inhibition of DNA replication and induction of �phase cell cycle arrest by G-rich oligonucleotides. J Biol Chem, 2001;276:43221-30}} ) .
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