( frequently in life. Walker and co...)Common enzyme is a key player in DNA repair

Walker and colleagues found that DinB's unique ability to repair DNA damage extends to mice and archaea, an ancient and diverse group of single-celled organisms. In nearly every organism, they believe, the same specialized enzyme is poised to patch over a certain kind of blemish so that it does not permanently damage the genome.

The DinB gene and its protein product were first discovered in Walker's lab in 1980, long before scientists knew anything about translesion polymerases. Then graduate student Cynthia Kenyon, now a biologist at University of California, San Francisco who has done groundbreaking work on the genetic basis of aging in worms, systematically identified the genes turned on in bacteria exposed to DNA damaging agents, the so-called SOS response. Kenyon named the damaged-inducible (Din) genes in order of discovery, and DinB was the second one she found.

"Knocking it out didn't seem to have an obvious effect ," Walker said. "We couldn't find anything interesting in the mutant bacteria." Since then, the known DinB family has grown to include five related proteins in bacteria, 10 in yeast, and four in people.

"We found it 25 years ago," said Walker about DinB, "and we're just now finding out what it does."