IFA to show that HCMV IE1 cannot protect mPML, or that MCMV IE1 cannot protect hPML, from degradation by ICP0. MRC-5 cells were cotransfected with plasmids expressing YFP-ICP0 and GFP-mIE1 (MCMV IE1) (upper) or NIH 3T3 cells were cotransfected with plasmids expressing YFP-ICP0 and GFP-hPML (lower) for 24 h. IFA was performed to visualize PML in purple, ICP0 in red, GFP in green, and DAPI in blue. Bar, 10 μm.