Double-strand breaks from a radical commonly produced by DNA-damaging agents

Area of Science:

• Biochemistry
• Molecular Biology
• Radiation Chemistry

Background:

• Double-strand breaks (DSBs) are highly toxic DNA lesions.
• Molecules causing DSBs are cytotoxic and rare compared to single-strand break inducers.
• A C4'-radical was recently identified as a DSB inducer under aerobic conditions.

Purpose of the Study:

• To elucidate the mechanism by which peroxyl radicals induce DNA double-strand breaks.
• To investigate the role of C4' and C3' positions in complementary strand damage.
• To determine the effect of thiols on peroxyl radical-induced DNA damage.

Main Methods:

• Chemical analysis of DNA damage mechanisms.
• Investigating radical reactions under aerobic conditions.
• Assessing the impact of thiols as radical scavengers.

Main Results:

• Peroxyl radicals initiate complementary strand damage via C4'-hydrogen atom abstraction.
• C3'-peroxyl radicals appear more efficient in inducing complementary strand damage than C4'-peroxyl radicals.
• Complementary strand hydrogen atom abstraction by peroxyl radicals is effectively quenched by thiols.

Conclusions:

• A novel mechanism for DSB formation involving peroxyl radicals and complementary strand damage is proposed.
• The findings suggest a potential contribution of this mechanism to DSB yields from ionizing radiation.
• Thiol-mediated quenching offers insights into radioprotective strategies.