Elledge’s group studied human cells in culture and mapped their response to ionizing radiation and ultraviolet light. Specifically, the group looked to see which proteins in the cell were chemically altered by the enzymes ATM and ATR, finding 900 sites on 700 proteins that changed in response to DNA damage. The discovery that so many proteins are involved in the process, Elledge said, was a big surprise.

Despite the abuse our DNA endures, our individual genomes usually stay basically intact because DNA has a remarkable capacity for repair. Our cells have built-in, highly efficient machinery that finds and fixes “genetic typos.”
…
Researchers have learned much about the complex genetic machinery that cells deploy to fix broken, cut, mutated, and misplaced genetic materials. Out of that evolving understanding has emerged a deeper awareness that DNA is truly dynamic and that responses to genetic damage are nearly as fundamental to life—and health—as is the genetic code itself.