The proposed mechanism of action:

Turns out that DdrC scans for breaks along the DNA and when it detects one it snaps shut—like a mousetrap. This trapping action has two key functions. He explains, "It neutralizes it (the DNA damage), and prevents the break from getting damaged further. And it acts like a little molecular beacon. It tells the cell 'Hey, over here. There's damage. Come fix it.'"

Interesting stuff.