(d) HeLa cells were transfected with plamsids encoding GFP-IRGMd, GFP-IRGMDS47N or YFP-IRGMb (vector encoding GFP only was transfected as a control), and after 48 h were stained with propidium iodide (PI). Percentages of GFP+ or YFP+ cells that were also PI+ were quantified. 