The wee1 protein kinase is required for radiation-induced mitotic delay

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Abstract
CELLULAR feedback or 'checkpoint' mechanisms maintain the order of completion of essential, cell-cycle related functions1–3. In the budding yeast, for example, theRAD9 gene product is required to delay progression into mitosis in response to DNA damage2,4–6. Similarly, in fission yeast, the cdc25 and cdc2 gene products influence the ability of cells to delay mitosis in response to the inhibition of DNA synthesis7. Because these two checkpoint controls regulate the same event, mitosis, we observed the effect of γ-irradiation on cell cycle progression in fission yeast, to test whether the two controls require the same cell-cycle regulatory elements. We show that γ-radiation-induced mitotic delay requires functional wee1 protein kinase but does not seem to involve the cdc25 pathway. Mitotic delay in response to DNA damage is thus distinct from the delay induced by inhibition of DNA synthesis, which involves cdc25 but is not dependent on wee1.