Nuclear translocation of the catalytic component of DNA-dependent protein kinase upon growth stimulation in normal human T lymphocytes.

DNA-dependent protein kinase (DNA-PK), consisting of the 470-kDa catalytic component (DNA-PKcs) and the DNA-binding regulatory component Ku protein (p70/p80), catalyzes phosphorylation of a variety of DNA replication/transcription/repair factors in the presence of double-stranded DNA. In the resting states of human peripheral blood mononuclear cells, DNA-PK activity and the protein level of DNA-PKcs were very low in the nuclear extracts, but they were high in the whole cell extracts. Depending upon proliferation of the T lymphocytes, DNA-PK activity and the protein level of DNA-PKcs in the nuclear extracts greatly increased. Immunocytochemical analysis suggested translocation of DNA-PKcs from the cytoplasm to the nucleus upon growth stimulation in the T lymphocytes.