The cellular 68,000-Mr protein kinase is highly autophosphorylated and activated yet significantly degraded during poliovirus infection: implications for translational regulation.
We investigated the possible translational regulatory roles played by the interferon-induced, double-stranded-RNA-activated protein kinase (P68) and its natural substrate, eucaryotic initiation factor 2 (eIF-2), in poliovirus-infected cells. We demonstrated that protein kinase P68 was both highly autophosphorylated and activated during poliovirus infection. In accordance with these results, immunoprecipitation analysis revealed that phosphorylation of the endogenous eIF-2 alpha subunit also increased in poliovirus-infected cells. We found that double-stranded RNA synthesized during infection likely induced the high levels of P68 autophosphorylation. To determine whether the increase in kinase activity also could be attributed to induction of P68 synthesis, physical levels of protein kinase were measured. It was unexpectedly found that P68 protein levels did not increase but rather dramatically declined in poliovirus-infected cells. Pulse-chase experiments confirmed that the protein kinase was significantly degraded during virus infection. We corroborated our in vivo observations by developing an in vitro assay for P68 degradation using cell extracts. The possible consequences of P68 degradation and increased eIF-2 alpha phosphorylation for protein synthesis regulation in poliovirus-infected cells are discussed.
Black
T L
TL
Department of Microbiology, School of Medicine, University of Washington, Seattle 98195.
Safer
B
B
Hovanessian
A
A
Katze
M G
MG
D004789:Enzyme Activation; D015852:Eukaryotic Initiation Factor-2; D005786:Gene Expression Regulation; D006367:HeLa Cells; D008970:Molecular Weight; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017955:Poliovirus / Q000235:genetics*; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*
D015852:Eukaryotic Initiation Factor-2; D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011506:Proteins; D011494:Protein Kinases