DNA-dependent protein phosphorylation activity in Xenopus is coupled to a Ku-like protein.
DNA-dependent protein kinase (DNA-PK) is a nuclear enzyme and functions as a serine/threonine kinase that has been well characterized in both the human and the mouse. The regulatory subunit of DNA-PK is the Ku autoantigen. To demonstrate that a Ku-like protein is present in Xenopus oocytes, we used immunoprecipitation analysis with a monoclonal antibody raised against human Ku antigen and autoimmune serum containing anti-Ku antibodies. Metabolic labeling studies indicate that the Ku-like protein is synthesized mainly in late vitellogenic oocytes. By using a specific peptide substrate for DNA-PK, we demonstrate the activity of a DNA-dependent protein kinase in oocyte extracts. The kinase activity requires the Ku-like protein, since extracts depleted of Ku protein by immunoadsorption with human anti-Ku antibodies fail to demonstrate the DNA-dependent phosphorylation activity. The increased enzyme activity in vitellogenic oocytes may be correlated to the increased levels of Ku protein observed in these oocytes compared to the pre- and early vitellogenic oocytes.
Kanungo
J
J
Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta 30912-3175, USA.
Cameron
R S
RS
Takeda
Y
Y
Hardin
J A
JA
D000595:Amino Acid Sequence; D000818:Animals; D034961:Antigens, Nuclear; D001323:Autoantibodies / Q000276:immunology; D001324:Autoantigens / Q000276:immunology / Q000378:metabolism; D004265:DNA Helicases; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000201:enzymology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000276:immunology / Q000378:metabolism*; D014982:Xenopus laevis
D034961:Antigens, Nuclear; D001323:Autoantibodies; D001324:Autoantigens; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen