irradiation. Immediately prior to irradiation, media was aspirated and the
cells were briefly washed with dPBS. With lids and dPBS removed, culture
plates containing the cells were exposed directly to UV-C radiation in a
254nm UV oven (CL-1000S UV crosslinker, UVP), then media was replenished.
All experiments here involved two equal doses of UV radiation, 24 hours
apart. Reported radiation doses are the total combined dose from two
treatments. Unless otherwise indicated, 48 hours following the terminal
dose, cells were trypsinized and resuspended in serum-free media for flow
cytometry analysis or sorting.