p56/p53lyn tyrosine kinase activation in mammalian cells treated with mitomycin C.

Abstract

The present studies have examined the effects of mitomycin C (MMC), a genotoxic alkylating agent, on the activation of Src-like protein tyrosine kinases in HL-60 myeloid leukemia cells. The results demonstrate no detectable induction of p59fyn or pp60c-src activity. The response of HL-60 cells to MMC however was associated with rapid activation of p56/p53lyn. Similar findings were obtained with other alkylating agents such as nitrogen mustard and cis-platinum. Activation of p56/p53lyn was associated with increased autophosphorylation on tyrosine and sensitivity to the tyrosine kinase inhibitors herbimycin A and genistein. Studies with a glutathione S-transferase-Lyn fusion protein were performed to explore the potential significance of p56/p53lyn activation. Analysis of the adsorbates demonstrates interaction of Lyn with the cell cycle regulatory protein, p34cdc2. Coimmunoprecipitation studies further confirmed the association of p56/p53lyn and p34cdc2 in MMC-treated cells. We also demonstrate that p34cdc2 undergoes increased phosphorylation on tyrosine following MMC exposure and that p56/p53lyn phosphorylates the Tyr-15 site of p34cdc2 in vitro. These findings indicate that the cellular response to MMC includes activation of p56/p53lyn and that this event may contribute to signals transduced by the DNA damage-dependent mitotic checkpoint.