Figure 4.

PKR activity tested in vitro on peritubular and Sertoli cell extracts. In vitro phosphorylation of PKR was performed after partial purification of the protein on poly (rI)–poly (rC) agarose, as described in Materials and Methods. Products were then analyzed on a 7.5% polyacrylamide gel (a, peritubular cells, P; b, Sertoli cells, S). Cells were stimulated or not (C) with IFN α (50, 275, and 500 U/ml) or IFN γ (10 and 100 U/ml) for 14 h, or with Sendai virus (V100 and V500 U/ml) for 28 h. The positive control is represented by murine 3T3 cells (3T3), and the autoradiography shown is representative of three totally independent culture and Northern blot experiments.