Heat shock protein 70 binds to human apurinic/apyrimidinic endonuclease and stimulates endonuclease activity at abasic sites

The interaction of human heat shock protein 70 (HSP70) with human apurinic/ apyrimidinic endonuclease (HAP1) was demonstrated by coimmunoprecipitation. A combination of HSP70 and HAP1 also caused a shift in the electrophoretic mobility of a DNA fragment containing an apurinic/apyrimidinic site. The f unctional consequence of the HSP70/HAP1 interaction was a 10-100-fold enhan cement of endonuclease activity at abasic sites. The physical and functiona l interaction between HSP70 and HAP1 did not require the addition of ATP. T he association of HSP70 and a key base excision repair enzyme suggests a ro le for heat shock proteins in promoting base excision repair. These finding s provide a possible mechanism by which HSP70 protects cells against oxidat ive stress.