title: Protein synthesis in BHK-21 cells infected with semliki forest virus.
abstract: [3H]leucine-labeled proteins synthesized in BHK-21 cells infected with Semliki Forest virus were fractionated by polyacrylamide gel electrophoresis (PAGE). Cellular and virus-specific proteins were identified by difference analysis of the PAGE profiles. The specific activity of intracellular [3H-A1leucine was determined. Two alterations of protein synthesis, which develop with different time courses, were discerned. (i) In infected cultures an inhibition of overall protein synthesis to about 25% of the protein synthesis in mock-infected cultures develops between about 1 and 4 h postinfection (p.i.). (ii) The relative amount of virus-specific polypeptides versus cellular polypeptides increases after infection. About 80% of the proteins synthesized at 4 h p.i. are cellular proteins. Since significant amounts of nontranslocating robosomes in polyribosomes were not detected up to 7 h p.i., the inhibition of protein synthesis is not caused by inactivation of about 75% of all polyribosomes but by a decreased protein synthetic activity of the majority of polyribosomes. Indirect evidence indicates that an inhibition of elongation and/or release of protein synthesis develops in infected cells, which is sufficient to account for the observed inhibition of protein synthesis. Inhibition of over-all protein synthesis developed when virus-specific RNA began to accumulate at the maximal rate. This relationship was observed during virus multiplication at 37, 30, and 25 C. A possible mechanism by which synthesis of virus-specific RNA in the cytoplasm could inhibit cellular protein synthesis is discussed. Indirect evidence and analysis of polyribosomal RNA show that the increased synthesis of virus-specific protein is brought about by a substitution of cellular by viral mRNA in the polyribosomes.
mesh_terms: D002460:Cell Line; D010452:Peptide Biosynthesis; D010441:Peptide Chain Elongation, Translational; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012335:RNA, Ribosomal / Q000096:biosynthesis; D012367:RNA, Viral / Q000096:biosynthesis; D012672:Semliki forest virus / Q000254:growth & development* / Q000378:metabolism; D014764:Viral Proteins / Q000096:biosynthesis*; D014779:Virus Replication
chemical_list: D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012367:RNA, Viral; D014764:Viral Proteins