Expression of DNA-dependent protein kinase in human granulocytes.
Human polymorphonuclear leukocytes (PMN) have been reported to completely lack of DNA-dependent protein kinase (DNA-PK) which is composed of Ku protein and the catalytic subunit DNA-PKcs, needed for nonhomologous end-joining (NHEJ) of DNA double-strand breaks. Promyelocytic HL-60 cells express a variant form of Ku resulting in enhanced radiation sensitivity. This raises the question if low efficiency of NHEJ, instrumental for the cellular repair of oxidative damage, is a normal characteristic of myeloid differentiation. Here we confirmed the complete lack of DNA-PK in PMN protein extracts, and the expression of the truncated Ku86 variant form in HL-60. However, this degradation of DNA-PK was shown to be due to a DNA-PK-degrading protease in PMN and HL-60. In addition, by using a protease-resistant whole cell assay, both Ku86 and DNA-PKcs could be demonstrated in PMN, suggesting the previously reported absence in PMN of DNA-PK to be an artefact. The levels of Ku86 and DNA-PKcs were much reduced in PMN, as compared with that of the lymphocytes, whereas HL-60 displayed a markedly elevated DNA-PK concentration. In conclusion, our findings provide evidence of reduced, not depleted expression of DNA-PK during the mature stages of myeloid differentiation.
Sallmyr
Annahita
A
Department of Medical Microbiology, Lund University, Malmo University Hospital, S-205 02 Malmo, Sweden.
Miller
Anna
A
Gabdoulkhakova
Aida
A
Safronova
Valentina
V
Henriksson
Gunnel
G
Bredberg
Anders
A
D034961:Antigens, Nuclear / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics*; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D006098:Granulocytes / Q000201:enzymology*; D018922:HL-60 Cells; D006801:Humans; D020014:K562 Cells; D000072200:Ku Autoantigen; D008214:Lymphocytes / Q000378:metabolism; D008970:Molecular Weight; D009504:Neutrophils / Q000201:enzymology*; D009687:Nuclear Proteins; D010447:Peptide Hydrolases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020298:U937 Cells; D015854:Up-Regulation / Q000235:genetics
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D010447:Peptide Hydrolases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen