METHOD. Murine lens epithelial TN4-1 cells were treated with IFN. Apoptosis was measured using annexin V-FITC and propidium iodide (PI) staining, and DNA fragmentation. IFN–inducible mRNA and protein expressions were measured by RT-PCR and Western blot analysis. Caspase activities were measured using colorimetric substrates and poly (ADP ribose) polymerase (PARP) cleavage. The effect of proteasome inhibition was tested with MG132 and lactacystin.