The DNA-dependent protein kinase: requirement for DNA ends and association with Ku antigen.
The DNA-dependent protein kinase (DNA-PK) phosphorylates Sp1 and several other nuclear proteins. Here, we show that Sp1 and the DNA-PK must be colocalized on the same DNA molecule for efficient phosphorylation to occur. Interestingly, we find that the DNA-PK binds to and is activated by the ends of DNA molecules. Furthermore, we show that the DNA binding properties of the DNA-PK are identical to those of Ku, a well-characterized human autoimmune antigen. We demonstrate that the DNA-PK can be fractionated into two components, one of which is Ku and the other of which is a polypeptide of approximately 350 kd. DNA cross-linking and coimmunoprecipitation studies indicate that the catalytic 350 kd DNA-PK component is directed to DNA by protein-protein interactions with Ku. The implications of the unusual DNA binding mode and multicomponent nature of the DNA-PK are discussed.
Gottlieb
T M
TM
Wellcome/CRC Institute, Cambridge, England.
Jackson
S P
SP
D034961:Antigens, Nuclear; D001483:Base Sequence; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000378:metabolism
D034961:Antigens, Nuclear; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016329:Sp1 Transcription Factor; D004247:DNA; D011494:Protein Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen