Mechanism of interferon action: eIF-2 alpha phosphatase in interferon-treated mouse fibroblasts is double-stranded...

The effect of double-stranded RNA on the dephosphorylation of purified, 32P-labeled eIF-2 was examined in cell-free extracts prepared from interferon-treated mouse L929 cells. Dephosphorylation of the alpha subunit of eIF-2 occurred at comparable rates in the presence and in the absence of reovirus dsRNA. By contrast, the beta subunit of eIF-2 was not dephosphorylated to any significant extent in either the presence or the absence of dsRNA. These results indicate that the enhanced phosphorylation of eIF-2 alpha observed in IFN-treated systems in the presence of double-stranded RNA (dsRNA) is indeed caused by an activation of a protein kinase rather than to an inhibition of a phosphoprotein phosphatase by the dsRNA.