MU2 and Double Strand Break Repair Figure 3. MU2 forms IRIF in S2 cells. (A) S2 cells were transiently transfected with pAGW-MU2 (N-terminal eGFP tag), irradiated with 25 Gy at 5 Gy/min 24 hrs after transfection, and fixed immediately at the termination of treatment. Control S2 cells on the left expressing eGFP-MU2 (green) and stained with cH2Av (red). After irradiation, shown in the middle and right panels, MU2 localized to distinct foci, which co-localized with cH2Av as observed in the merged image (yellow). (B) S2 cells were irradiated with 25 Gy, and stained with anti-MU2 (green) and rabbit anti-cH2Av (red) antibodies. Unirradiated S2 cells are shown on the left; irradiated S2 cells are shown in the middle and right panels. After irradiation, MU2 protein localized to distinct foci and co-localized with cH2Av. (C) Kinetics of the formation of MU2 foci were studied at different intervals after irradiation. MU2 foci appear immediately after irradiation and co-localize with cH2Av. doi:10.1371/journal.pgen.1000473.g003 PLoS Genetics | www.plosgenetics.org 6 May 2009 | Volume 5 | Issue 5 | e1000473