Radiation emitted from radioactive materials induces a variety of chemical modifications of DNA in a living cell by energy deposition along a radiation-track. DNA-modification (DNA damage) is thought to be one of main causes of radiobiological effects such as carcinogenesis. On the other hand, most of DNA damages are known to be enzymatically repaired by DNA-repair proteins in a living cell. The “DNA repair” is one of the most conservative characteristics for living system from E.coli to human cells. Many enzymatic processes are involved in the DNA repair. The protein-protein reactions are like a “network” system. Over 90% of DNA-double strand break, which is one of the most severe DNA damage induced even by low LET radiation, is efficiently rejoined. However, several DNA modifications still remain as “unrepaired damage”, and the molecular processes has not fully characterized yet.

Schematic figure of radiation damage to DNA