Can DNA breaks be repaired?

• Position: Chromosomes

A new microscopic assay has been developed by scientists at the University of North Carolina at Chapel Hill that, for the first time, allows them to see DNA breaks in chromosomes in living cells following damage to those complex, gene-filled structures. Their success is exciting because the assay should become a powerful aid for boosting understanding of chromosome damage and how it is repaired naturally or might be repaired therapeutically, notes Kerry S. Bloom, professor of biology. Chromosome damage leads to, at a minimum, hundreds of fatal or debilitating illnesses each year.

"In the course of this work, we discovered that, when breaks occur in either one or both strands of DNA, which is a complex, double-stranded, helical molecule, the chromosomes do not fragment," Bloom explains. "Proteins are recruited very quickly to the sites of DNA damage, and they keep the chromosome intact. This was hypothesized but never shown before. We also identified some of those specific proteins."

Human cells contain an amazing amount of DNA, which produces proteins for countless tasks in the body. "In fact, if you took all of the DNA in your cells and stretched it out, it would go to the sun and back. That is awesome," marvels Bloom.

"This is the first [study] that distinguishes breaks in chromosomes versus breaks in DNA," Bloom points out. "Chromosomal breaks are important in many...