ACTIVATION OF NUCLEAR FACTOR KAPPA-B IN HUMAN LYMPHOBLASTOID-CELLS BYLOW-DOSE IONIZING-RADIATION

Nuclear factor kappa B (NF-kappa B) is a pleiotropic transcription fac tor which is involved in the transcriptional regulation of several spe cific genes. Recent reports demonstrated that ionizing radiation in th e dose range of 2-50 Gy results in expression of NF-kappa B in human K G-1 myeloid leukemia cells and human B-lymphocyte precursor cells; the precise mechanism involved and the significance are not yet known. Th e present report demonstrates' that even lower doses of ionizing radia tion, 0.25-2.0 Gy, are capable of inducing expression of NF-kappa B in EBV-transformed 244B human lymphoblastoid cells. These results are in a dose range where the viability of the cells remains very high. Afte r exposure to Cs-137 gamma rays at a dose rate of 1.17 Gy/min, a maxim um in expression of NF-kappa B was seen at 8 h after a 0.5-Gy exposure . Time-course studies revealed a biphasic time-dependent expression af ter 0.5-, 1- and 2-Gy exposures. However, for each time examined, the expression of NF-kappa B was maximum after the 0.5-Gy exposure. The ex pression of the p50 and p65 NF-kappa B subunits was also shown to be r egulated differentially after exposures to 1.0 and 2.0 Gy.