53BP1 turnover is accelerated upon irradiation.

<p><b>A</b>. Cycloheximide (100 µg/mL) was added to MCF7 cells with or without irradiation (10 Gy) and total cell lysates were prepared in SDS containing buffer according to the indicated time course (0, 0.5 and 4 h) and analyzed by immunoblotting as indicated. <b>B</b>. 53BP1 protein signal in immunoblot in A was measured by densitometry in each sample.