The interaction of zinc(II) ions with antiparallel-stranded d(GA)n DNA homoduplexes.
In the presence of specific metal-ions (namely zinc but also cadmium, cobalt and manganese), d(GA x TC)n DNA sequences can form non-B-DNA conformations. At low metal-ion concentration they form [GA(GA x TC)] intramolecular triplexes but, upon increasing the metal concentration, the formation of (GA x GA) intramolecular hairpins is detected. In this paper we address the question of the specific effects of zinc on the structure of the d(GA x TC)n sequences. In the presence of zinc, the DMS-reactivity of the (GA x GA) hairpins is strongly reduced suggesting a direct interaction of the metal-ion with the N7-group of the guanines. This effect is specific for antiparallel-stranded d(GA)n homoduplexes. No such strong decrease in DMS-reactivity is observed in B-DNA duplexes or in d(GGA)n and d(GGGA)n homoduplexes. In addition, the thermal stability of antiparallel-stranded d(GA)n homoduplexes increases in the presence of zinc. On the contrary, the melting temperature of similar B-DNA molecules decreases upon increasing the zinc concentration. Altogether, these result indicate that zinc plays an specific role on the stabilization of the (GA x GA) intramolecular hairpins.
Ortiz-Lombardía
M
M
Departament de Biologia Molecular i Cellular, Centre d'Investigació i Desenvolupament, Barcelona, Spain.
Jiménez-García
E
E
García-Bassets
I
I
Azorín
F
F
D002413:Cations, Divalent; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D019175:DNA Methylation; D007477:Ions; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry / Q000378:metabolism*; D013463:Sulfuric Acid Esters / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
D002413:Cations, Divalent; D007477:Ions; D011089:Polydeoxyribonucleotides; D013463:Sulfuric Acid Esters; C046661:poly(d(TC)).poly(d(GA)); D004247:DNA; D015032:Zinc; C007482:dimethyl sulfate