How DNA Avoids Damage from UV Light

In the same week that the U.S. surgeon general issued a 101-page report about the dangers of skin cancer, researchers at Montana State University (MSU) published a paper breaking new ground on how DNA – the genetic code in every cell – responds when exposed to ultraviolet (UV) light. The findings advance fundamental understanding of DNA damage by the UV rays found in sunlight. This damage can lead to skin cancer, aging, and some degenerative eye diseases. "Our paper advances foundational knowledge about how DNA responds to UV radiation. In our experiments, we observe the earliest events immediately after DNA is energized by UV radiation. These events determine whether or not DNA is damaged," said one of the paper's co-authors, Dr. Bern Kohler, an MSU professor in the Department of Chemistry and Biochemistry. DNA is built like a staircase and carries genetic instructions that are unique to each person. It's very hardy and generally able to stand up to ultraviolet rays, but UV rays sometimes cause mutations. UV exposure is a major cause of skin cancer, and while there are nearly 5 million cases of skin cancer each year in the U.S. alone – and 9,000 related deaths – the numbers would be far worse if DNA were more easily damaged. "UV is actually very damaging, yet our DNA is damaged less than expected," Dr. Kohler said. "In the early evolution of life on Earth when there was no ozone layer, the amount of UV would have been far higher and yet life, and the DNA that is central to life, survived. We've been trying to understand the molecular mechanisms that make DNA resist UV damage." In a paper published July 28, 2014 in the online version of the scientific journal PNAS, Dr.