Stimulation of the DNA unwinding activity of human DNA helicase II/Ku by phosphorylation.
The Ku autoantigen is a heterodimeric protein of 70- and 83-kDa subunits, endowed with duplex DNA end-binding capacity and DNA helicase activity (Human DNA Helicase II, HDH II). HDH II/Ku is well established as the DNA binding component, the regulatory subunit as well as a substrate for the DNA-dependent protein kinase DNA-PK, a complex involved in the repair of DNA double-strand breaks and in V(D)J recombination in eukaryotes. The effects of phosphorylation by this kinase on the helicase activity of Escherichia coli-produced HDH II/Ku were studied. The rate of DNA unwinding by recombinant HDH II/Ku heterodimer is stimulated at least fivefold upon phosphorylation by DNA-PK(cs). This stimulation is due to the effective transfer of phosphate residues to the helicase rather than the mere presence of the complex. In vitro dephosphorylation of HeLa cellular HDH II/Ku caused a significant decrease in the DNA helicase activity of this enzyme.
International Centre for Genetic Engineering and Biotechnology, Institutional Services and Biosafety, Padriciano 99, 34012 Trieste, Italy. ochem@icgeb.org
Alexander E
AE
Ochem
Hocine
H
Rechreche
Doris
D
Skopac
Arturo
A
Falaschi
D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D009690:Nucleic Acid Conformation; D010766:Phosphorylation
D004247:DNA; D004265:DNA Helicases