5' to 3' single strand DNA exonuclease activity in a preparation of human Ku protein.
We describe a novel 5' to 3' single-strand exonuclease activity exhibited by a Ku preparation purified from a human cell line. The enzyme removes 5' single-strand extensions from duplex DNA molecules. The exonuclease and helicase activities respond reciprocally to changes in ATP concentrations: Nuclease activity is inhibited at the ATP concentrations that are optimal for the helicase. The exonuclease activity does not require divalent cations. The potential implications of the exonuclease activity findings for repair of double-strand breaks and recombination processes are discussed.
Morozov
V E
VE
Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA. viktorm@box-v.nih.gov
Fuller
B G
BG
D000818:Animals; D034961:Antigens, Nuclear; D016367:Baculoviridae / Q000235:genetics; D004265:DNA Helicases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004330:Drosophila / Q000821:virology; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D000072200:Ku Autoantigen; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen