Semliki Forest virus capsid protein acts as a pleiotropic regulator of host cellular protein synthesis.
The Semliki Forest virus capsid (C) protein was introduced into various target cells by electroporation-, liposome-, and erythrocyte-ghost-mediated delivery. Data are presented which show that the incorporated C protein is biologically active and, at low concentrations (10(3) to 10(4) molecules per cell), markedly induces host cellular protein synthesis (average value, up to 90%). On the other hand, high concentrations (10(5) to 10(6) molecules per cell) led to a significant inhibition (average value, up to 60%). The cellular response to C protein was found to be identical in P3X63Ag8 suspension cells, CV-1 cells, and GpBind4 cells. Following electroporation-mediated delivery of C-protein molecules, both induction and repression of cellular protein synthesis were immediate, whereas with liposome-mediated delivery these events were delayed by about 1 h. Maximum stimulation and repression occurred between 0 and 1 h after delivery of C protein and decreased thereafter to reach control values at about 4 h. The analysis of the proteins synthesized suggests that low amounts of microinjected C protein are responsible for the induction of classes with specific Mrs, whereas high amounts lead to an inhibition of overall protein synthesis.
Elgizoli
M
M
Institute of Hygiene and Medical Microbiology, University of Berne, Switzerland.
Dai
Y
Y
Kempf
C
C
Koblet
H
H
Michel
M R
MR
D000818:Animals; D002213:Capsid / Q000302:isolation & purification / Q000502:physiology*; D002460:Cell Line; D002472:Cell Transformation, Viral; D004910:Erythrocyte Membrane / Q000378:metabolism; D005809:Genes, Regulator; D007700:Kinetics; D008081:Liposomes; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000096:biosynthesis; D014176:Protein Biosynthesis; D012672:Semliki forest virus / Q000235:genetics*
D008081:Liposomes; D009363:Neoplasm Proteins