EFFECT OF WORTMANNIN AND 3-AB ON G(2) PHASE ARREST AND TRANSIENT FAILURE TO ACTIVATE MPF INDUCED BY IONIZING IRRADIATION

Active mitosis promoting factor (MPF) composed of p34(cdc2) With cycli n B1 is required for the cell cycle transition from G(2) to M phase. R ecent studies have demonstrated that ionizing radiation (IR) exposures associated with inhibition of p34(cdc2) activity was the mechanism of G(2) arrest. At low dose, IR causes transient failure to dephosphoryl ate p34(cdc2) instead of suppression of cyclin B or MPF formation of c yclin B with p34(cdc2) complex. But the signaling events that regulate p34(cdc2) in irradiated cells remain unclear. This note demonstrates that PI3 kinase family inhibitor wortmannin (wort) and PARP specific i nhibitor 3-AB can reduce the G(2) arrest induced by 2Gy gamma-ray. Imm unoprecipitation studies demonstrate that wort and 3-AB can facilitate dephosphorylation of p34(cdc2) in G(2) phase arrest induced by radiat ion. These findings suggest that wort sensitive pathway and PARP may b e involved in initiating the signal transduction of G(2) phase arrest caused by IR.