Figure 4.

Enzyme activity of PKR in non-stimulated and IFN-α stimulated beta TC3 and alpha TC3 cells. Beta TC3 and alpha TC3 cells were incubated with or without addition of 500 U/mL of IFN-α into the medium for 24 hours in three independent experiments. The lysates were subjected to an autophosphorylation assay with γ ³²P-ATP. Incubation time was 1 hour. Proteins were fractionated by 12% SDS-PAGE and radioactive bands were visualized by autoradiography. After the gels were dried, the protein bands were cut and the radioactivity was quantitated in a scintillation counter.