Article

The DNA-dependent protein kinase is inactivated by autophosphorylation of the catalytic subunit.

Department of Biological Sciences, University of Calgary, 2500 University Drive, N.W., Calgary, Alberta, T2N 1N4, Canada.
Journal of Biological Chemistry (Impact Factor: 4.6). 05/1996; 271(15):8936-41. DOI: 10.1074/jbc.271.15.8936
Source: PubMed

ABSTRACT The DNA-dependent protein kinase (DNA-PK) requires for activity free ends or other discontinuities in the structure of double strand DNA. In vitro, DNA-PK phosphorylates several transcription factors and other DNA-binding proteins and is thought to function in DNA damage recognition or repair and/or transcription. Here we show that in vitro DNA-PK undergoes autophosphorylation of all three protein subunits (DNA-PKcs, Ku p70 and Ku p80) and that phosphorylation correlates with inactivation of the serine/threonine kinase activity of DNA-PK. Significantly, activity is restored by the addition of purified native DNA-PKcs but not Ku, suggesting that inactivation is due to autophosphorylation of DNA-PKcs. Our data also suggest that autophosphorylation results in dissociation of DNA-PKcs from the Ku-DNA complex. We suggest that autophosphorylation is an important mechanism for the regulation of DNA-PK activity.

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