Iron chelators induce ubiquitin-independent degradation of CD1. A31N-ts20 cells were used because they have a temperature-sensitive E1 ubiquitin–activating enzyme which is active at 32°C, but is inactivated at 39°C, preventing ubiquitin-dependent proteasomal degradation. Cells were grown at 32°C or 39°C for 24 hours prior to the experiment. The medium was then removed and the cells were incubated for 24 hours at either temperature with control media or media containing DFO (250 μM), 311 (25 μM), or their Fe(III) complexes, namely DFO-Fe (250 μM) or 311-Fe (25 μM); Western analysis was then performed. Results shown are from a representative experiment from 3 performed.