Ionizing radiation shatters DNA into fragments, and it has long been thought that this is what makes it so dangerous for living organisms. Now, a research team led by M.J. Daly from the Uniformed Services University of the Health Sciences, Bethesda, MD, found a different explanation:
The degree of resistance against ionizing radiation is determined by the level of oxidative protein damage caused during irradiation and not by the damage of the DNA.
By irradiating Deinococcus radioduraans, a bacterium that can survive doses of ionising radiation thousands of times stronger than would kill a human, Daly's team found that the resilience of a cell's repair proteins is linked to the concentration of manganese ions in the cell.
The results of this research have been published March 20 in the open source journal PLOS Biology. Manganese (II) prevents oxidative damage to repair proteins and allows them to swing into action after radiation has damaged DNA.
The implication is that the degree of resistance is not depending on
the stability of DNA but on the functioning of repair proteins. In essence this means that it doesn't matter if the DNA is broken up, as long as it can be repaired by undamaged repair proteins.
Daly speculates that it may be possible to deliver Deinococcus repair proteins into animal cells and so increase radiation resistance. This could be useful in space travel, where radiation sickness is a potential problem on long interplanetary journey or could help cancer patients by reducing side-effects of radiation therapy. The original study
Michael J. Daly, Elena K. Gaidamakova, Vera Y. Matrosova, Alexander Vasilenko, Min Zhai, Richard D. Leapman, Barry Lai, Bruce Ravel, Shu-Mei W. Li, Kenneth M. Kemner, James K. Fredrickson, Protein Oxidation Implicated as the Primary Determinant of Bacterial Radioresistance,
PLoS Biol 5(4): e92 doi:10.1371/journal.pbio.0050092