Ar. Collins et al., THE KINETICS OF REPAIR OF OXIDATIVE DNA-DAMAGE (STRAND BREAKS AND OXIDIZED PYRIMIDINES) IN HUMAN-CELLS, Mutation research. DNA repair, 336(1), 1995, pp. 69-77
Single cell gel electrophoresis is a sensitive method for detecting DN
A strand breaks. Cells embedded in agarose are converted to nucleoids
by treating with detergent and high salt. DNA breaks render the nucleo
id DNA susceptible to extension by electrophoresis, forming 'comets'.
We find that when DNA breakage resulting from H2O2 treatment is examin
ed, freshly isolated normal human lymphocytes are relatively resistant
compared with transformed human cells. When incubated after treatment
with H2O2, HeLa cells repair most strand breaks within 1 h, and a sub
stantial fraction of the oxidised pyrimidines (detected by converting
them to DNA breaks with endonuclease III) within 4 h. However, lymphoc
ytes are less proficient at repair; during incubation for 4 h after tr
eatment with H2O2, no detectable removal of endonuclease III-sensitive
sites is seen. While the addition of deoxyribonucleosides promotes co
mpletion of repair of UV damage by lymphocytes, it has no significant
effect on repair of oxidative damage.