| CDC25B phosphorylation by Aurora A occurs at the G2 / M transition and is inhibited by DNA damage . ^^^ The STK15 / Aurora A kinase locally phosphorylates CDC25B on serine 353 at the centrosome during the G2 / M transition . ^^^ Upon activation of the G2 / M checkpoint by DNA damage , we demonstrate that Aurora A is not activated and consequently CDC25B is not phosphorylated . ^^^ We show that ectopic expression of Aurora A results in a bypass of the checkpoint that was partially overcome by a S353A mutant of CDC25B . ^^^ Finally , we show that bypass of the G2 / M checkpoint by the CHK 1 kinase inhibitor UCN 01 results in the activation of Aurora A and phosphorylation of CDC25B on S 353 . ^^^ |