Frog virus 3-induced translational shut-off: activation of an eIF-2 kinase in virus-infected cells.
Infection of susceptible fathead minnow or Friend erythroleukemia cells with either infectious or heat-inactivated frog virus 3 led to the rapid inhibition of cellular protein synthesis. As seen in other cells, translational shut-off was accompanied by the dissociation of polysomes, but not the degradation of irreversible inactivation of cellular mRNAs. In addition, lysates from cells infected with heat-inactivated FV3 showed a reduced capacity to synthesize protein and to form 43S pre-initiation complexes in vitro. These results indicate that the in vitro systems accurately reflected in vivo events, and suggest that translational shut-off occurred prior to the union of the 40S ribosomal subunit and the [eIF-2.GTP.Met tRNAi] ternary complex. To determine the basis for the translational block, lysates from mock- and FV3-infected cells were assayed in vitro for their ability to phosphorylate the alpha subunit of eIF-2. In contrast to lysates from mock-infected cells, lysates from cells infected with heat-inactivated or infectious FV3 readily phosphorylated the alpha subunit of eIF-2. Since phosphorylation of the alpha subunit of eIF-2 inhibits its catalytic utilization during polypeptide chain initiation, these findings suggest that translational shut-off mediated by FV3 may be due to activation of a kinase that selectively phosphorylates this key initiation factor.
Chinchar
V G
VG
Department of Microbiology, University of Mississippi Medical Center, Jackson 39216.
Dholakia
J N
JN
D000818:Animals; D002461:Cell Line, Transformed; D004789:Enzyme Activation; D007497:Iridoviridae / Q000502:physiology*; D010766:Phosphorylation; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D019892:eIF-2 Kinase
D012333:RNA, Messenger; D011494:Protein Kinases; D019892:eIF-2 Kinase