| Regulation of interferon induced protein kinase PKR : modulation of P58IPK inhibitory function by a novel protein , P52rIPK . ^^^ Conversely , introduction of P52rIPK into these strains resulted in restoration of both PKR activity and eIF 2alpha phosphorylation , concomitant with growth suppression due to inhibition of P58IPK function . ^^^ Furthermore , P52rIPK inhibited P58IPK function in a reconstituted in vitro PKR regulatory assay . ^^^ Our results demonstrate that P58IPK is inhibited through a direct interaction with P52rIPK which , in turn , results in upregulation of PKR activity . ^^^ |