Ku protein in human T and B lymphocytes: full length functional form and signs of degradation.
DNA-dependent protein kinase (DNA-PK) has been shown to take part in cell cycle regulatory signal transduction and in the repair of X-ray-induced DNA double-strand breaks. Functional DNA-PK is furthermore needed for the generation of antigen specificity during lymphocyte maturation. The Ku86 subunit of DNA-PK has been reported to exist in human B lymphocytes in a truncated form capable of binding to broken DNA but lacking the ability to activate the kinase function of DNA-PK. In the present work the Ku70 and Ku86 dimer proteins in T and B lymphocytes from human blood donors were analysed by immunoblotting and were observed apparently to be of full length. Also, nuclear protein extracted from B and non-B lymphocytes displayed DNA-dependent kinase activity. However, a minor fraction of Ku86 in lymphocytes was observed to be truncated with a molecular mass of approx. 70 kDa.
Sallmyr
A
A
Department of Medical Microbiology, Lund University, Malmö University Hospital, S-205 02, Malmö, Sweden.
Henriksson
G
G
Fukushima
S
S
Bredberg
A
A
D034961:Antigens, Nuclear; D001402:B-Lymphocytes / Q000378:metabolism*; D002460:Cell Line; D004265:DNA Helicases; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D008970:Molecular Weight; D009000:Monocytes / Q000378:metabolism; D009687:Nuclear Proteins / Q000032:analysis* / Q000737:chemistry; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*
D034961:Antigens, Nuclear; 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; D000072200:Ku Autoantigen