Activation of Src-like p56/p53lyn tyrosine kinase by ionizing radiation

Mammalian cells respond to ionizing radiation (IR) with cell cycle arrest, activation of DNA repair, and induction of early response genes. The present work has examined the involvement of Src-like protein-tyrosine kinases in the response of irradiated HL-60 myeloid leukemia cells. The results demonstrate little if any effect of IR on p59fyn, p56lck, and pp60c-src activity. In contrast, HL-60 cells responded to x-ray exposure with activation of p56/p53lyn. At a dose of 200 centigrays, induction of p56/p53lyn activity was detectable at 15 min. Doses as low as 50 centigrays were effective in activating p56/p53lyn. H2O2 and the scavenger N-acetylcysteine had no detectable effect on p56/p53lyn activation, while the protein-tyrosine kinase inhibitors, herbimycin and genistein, blocked induction by IR. The results also demonstrate that incubation of a glutathione S-transferase-Lyn fusion protein with lysates of irradiated HL-60 cells is associated with binding of the cell cycle regulatory protein, p34cdc2. The interaction of p56/p53lyn and p34cdc was confirmed in similar experiments with a glutathione S-transferase-Cdc2 fusion protein. Moreover, coimmunoprecipitation studies demonstrate the selective binding of activated p56/p53lyn to p34cdc2 in irradiated cells. These findings indicate that IR activates p56/p53lyn in HL-60 cells and that this tyrosine kinase may contribute to the regulation of p34cdc2.