Ku complex interacts with and stimulates the Werner protein

Werner syndrome (WS) is the hallmark premature aging disorder in which affe cted humans appear older than their chronological age. The protein WRNp, de fective in WS, has helicase function, DNA-dependent ATPase, and exonuclease activity. Although WRNp functions in nucleic acid metabolism, there is lit tle or no information about the pathways or protein interactions in which i t participates. Here we identify Ku70 and Ku86 as proteins that interact wi th WRNp. Although Ku proteins had no effect on ATPase or helicase activity, they strongly stimulated specific exonuclease activity. These results sugg est that WRNp and the Ku complex participate in a common DNA metabolic path way.