sentence1: A few studies have reported the control of APC/C by genotoxic stress in mammalian cells, Ionizing radiation was shown to activate the APC/C to degrade cyclin D1, which triggers an immediate p53-independent G1 arrest.
sentence2: In fact, genotoxic stresses such as ionizing radiation have been demonstrated to trigger rapid proteolysis of cyclin D1, leading to p53-independent G1 arrest.