Ku70 can translocate to the nucleus independent of Ku80 translocation and DNA-PK autophosphorylation.
Ku plays an important role in multiple nuclear processes, e.g., DNA repair, chromosome maintenance, and transcriptional regulation. Although some evidence suggests that the nuclear translocation of Ku plays a key role in regulating the function of Ku, the mechanism is poorly understood. Using the site-directed mutagenesis technique, we demonstrate here that Ku70 can translocate to the nucleus without heterodimerization with Ku80. The nuclear accumulation of Ku70 mutants of the nuclear localization signal, which retained their binding ability with Ku80, was diminished. On the other hand, Ku70 mutants which lacked the ability to bind with Ku80 could translocate to the nuclei. Human Ku70, when transfected, accumulated within the nuclei of hamster xrs-6 cells which had undetectable DNA-PK activity and Ku80. Ku70 and Ku80 mutants of DNA-PK phosphorylation sites showed normal heterodimerization and nuclear translocation. These findings also support the idea that Ku70 can translocate to the nucleus independent of DNA-PK autophosphorylation.
Koike
M
M
Genome Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan. m_koike@nirs.go.jp
Shiomi
T
T
Koike
A
A
D021581:Active Transport, Cell Nucleus; D000818:Animals; D034961:Antigens, Nuclear; D015153:Blotting, Western; D016466:CHO Cells; D002467:Cell Nucleus / Q000378:metabolism*; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D004265:DNA Helicases; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D000072200:Ku Autoantigen; D009154:Mutation / Q000235:genetics; D019913:Nuclear Localization Signals / Q000235:genetics / Q000502:physiology; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D011993:Recombinant Fusion 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; D000072200:Ku Autoantigen