Rnase a

Cell cycle phase distribution was measured by propidium iodide (PI) staining and flow cytometry. Cells were detached from the plate using Trypsin-EDTA Solution (Welgene), washed with DPBS, fixed in 70% ethanol at −20°C for 16 h, washed twice in DPBS, treated with RNase A (100 μg/mL) (BIOFACT, Cat. No. PE290-25h), and stained with 2 μg/mL PI (Thermo Scientific, Cat. No. P3566). Staining profiles indicative of cell cycle stage distribution were measured using a CytoFLEX flow cytometer (Beckman Coulter, Brea, CA, USA) and CytExpert software (Beckman Coulter). Results are presented as content histograms, with number of cells plotted on the y-axis and DNA content as measured by PI fluorescence on the x-axis.

Cells were irradiated with 0, 2, and 4 Gy dose of ionizing radiation, respectively. Then, 24 h later, irradiated Cells were trypsinized, washed in PBS, and fixed in 70% ethanol for 30 min on ice. Fixed cells were suspended in PI (BD biosciences) containing 0.1 mg/mL RNase A (BIOFACT, Daejeon, Korea); then, incubated at 37 °C for 15 min. DNA content was analyzed using a FACSCalibur flow cytometer (BD Bio-science) and the Flowjo software v7.6.1. (Flowjo, Ashland, OR, USA). At least 10,000 cells per replication were analyzed and two replicas were performed at each time point.