Identification and characterization of a protein found after X-irradiation in human T cell leukemia

An X-ray-induced protein in human T cell leukemia MOLT-4 cells is described. It was detected 4 hrs after irradiation by two dimensional gel electrophoresis and silver staining. The location is 41 kDa in the mass and 4.0 of pI. Its spots were collected from the gels and microsequenced. The protein was identified from its partial sequences as a set gene product, whose gene translocation previously was found in a case of acute undifferentiated leukemia. Polyclonal rabbit antibodies stained two spots, the 41 kDa (p 41) and the 42 kDa (p 42) proteins. Photoimage analyses of the silver-stained gels and Western blots indicated that the induction of p 41 was time dependent, starting 4 hrs after irradiation and reaching a plateau by 10 hrs, and was dose dependent between 1 and 10 Gy. p 41 appeared somewhat ahead of cell death, as determined by the dye exclusion test, but the role in that cell process has yet to be clarified.