SPECIFIC MUTATIONS NEAR THE AMINO-TERMINUS OF DOUBLE-STRANDED RNA-DEPENDENT PROTEIN-KINASE (PKR) DIFFERENTIALLY AFFECT ITS DOUBLE-STRANDED-RNA BINDING AND DIMERIZATION PROPERTIES

The amino-terminal region of the double-stranded (ds) RNA-dependent pr otein kinase, PKR, has been shown to mediate both dsRNA binding and pr otein dimerization, To critically examine if PKR dimerization is depen dent on dsRNA binding, we generated a series of mutants that are incap able of binding dsRNA. Some, but not all, of these mutants retained th e ability to dimerize, as shown by a two-hybrid transcriptional activa tion assay in vivo and a chemical cross-linking assay in vitro. These mutants were used further to demonstrate that the translational inhibi tory activity of PKR in vivo requires dsRNA binding; PKR mutants that dimerized but did not bind dsRNA could not inhibit the translation of a transfected reporter gene.