UPTON, NY -- In research that could help assess the radiation risks faced by astronauts, improve the cancer-killing potential of radiation therapy, and distinguish between DNA damage caused by normal living and that caused by low-level radiation, scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed a new way to detect and quantify varieties of radiation damage that previously could not be measured.

Scientists have long known that ionizing radiation, such as gamma rays and x-rays, can damage deoxyribonucleic acid (DNA), the genetic-code-carrying molecule that tells cells which proteins to make. The oxygen we breathe can cause damage, too. Most of the time, our bodies repair the damage we receive from everyday radiation sources such as sunlight and from oxygen. But unrepaired or incorrectly repaired damage can be lethal to cells or cause cancer.

"For years, people have been worried about the consequences of double strand breaks," says Betsy Sutherland, who leads the Brookhaven research team. These closely spaced breaks through both strands of the DNA double helix are known to be difficult for cells to repair. Scientists have also hypothesized that radiation might produce other forms of clustered damage on both DNA strands, like oxidation of the bases A, G, C, and T. Could these clustered damage sites be equally, or more, harmful? The problem with finding out, Sutherland says, is that no one has had a way to determine if radiation actually induces these kinds of damage, or to measure their frequencies and assess their repairability -- until now.

"We figured out how to do it," Sutherland says. The idea is fairly simple: Sutherland and her team use special enzymes supplied by collaborators in France that are designed to cut DNA strands at sites of specific kinds of damage. The team first irradiates the DNA (or cells in culture), then chops the DNA with the enzymes, and finally separates and counts the fragments on e
'"/>

Contact: Karen McNulty
kmcnulty@bnl.gov
631-344-8350
DOE/Brookhaven National Laboratory
10-Jul-2000