Radiolytic signature of Z-DNA.
Ionizing radiations induce various damages in DNA via the hydroxyl radical OH. generated by the radiolysis of water. We compare here the radiosensitivity of B- and Z-DNA, by using a Z-prone stretch included in a plasmid. In the supercoiled plasmid, the stretch is in the Z-form, whereas it is in the B-form when the plasmid is relaxed. Frank strand breaks (FSB) and alkali-revealed breaks (ARB) were located and quantified using sequencing gel electrophoresis. We show that B- and Z-DNA have the same mean sensitivity towards radiolytic attack, for both FSB and ARB. Nevertheless, the guanine sites are more sensitive, and the cytosine sites less sensitive in Z- than in B-DNA, leading to a characteristic signature of the Z-form. The comparison of experiments with the outcome of a Monte Carlo simulation of OH. radical attack suggests that transfer of initial damage from a guanine base to its attached sugar or the adjacent 3' cytosine is more important in Z-DNA than in B-DNA.
Tartier
L
L
Centre de Biophysique Moléculaire, CNRS, Orléans, France.
Michalik
V
V
Spotheim-Maurizot
M
M
Rahmouni
A R
AR
Sabattier
R
R
Charlier
M
M
D001483:Base Sequence; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D005609:Free Radicals; D006878:Hydroxides / Q000737:chemistry; D008969:Molecular Sequence Data; D009010:Monte Carlo Method; D010957:Plasmids
D005609:Free Radicals; D006878:Hydroxides; D004247:DNA; C031356:hydroxide ion