Visualization of complex DNA damage along accelerated ions tracks

¹ Joint Institute for Nuclear Research, Dubna, Russia
² Dubna State University, Dubna, Russia
³ University of Chemistry and Technology Prague, Prague, Czech Republic

^* Corresponding author: kruglyakovaea@bk.ru

Published online: 18 April 2018

Abstract

The most deleterious DNA lesions induced by ionizing radiation are clustered DNA double-strand breaks (DSB). Clustered or complex DNA damage is a combination of a few simple lesions (single-strand breaks, base damage etc.) within one or two DNA helix turns. It is known that yield of complex DNA lesions increases with increasing linear energy transfer (LET) of radiation. For investigation of the induction and repair of complex DNA lesions, human fibroblasts were irradiated with high-LET ¹⁵N ions (LET = 183.3 keV/μm, E = 13MeV/n) and low-LET ⁶⁰Co γ-rays (LET ≈ 0.3 keV/μm) radiation. DNA DSBs (γH2AX and 53BP1) and base damage (OGG1) markers were visualized by immunofluorecence staining and high-resolution microscopy. The obtained results showed slower repair kinetics of induced DSBs in cells irradiated with accelerated ions compared to 60Co γ-rays, indicating induction of more complex DNA damage. Confirming previous assumptions, detailed 3D analysis of γH2AX/53BP1 foci in ¹⁵N ions tracks revealed more complicated structure of the foci in contrast to γ-rays. It was shown that proteins 53BP1 and OGG1 involved in repair of DNA DSBs and modified bases, respectively, were colocalized in tracks of ¹⁵N ions and thus represented clustered DNA DSBs.