Identification of a cis-acting element required for shunt-mediated translational initiation of the Sendai virus Y proteins.
Shunting is a mechanism that permits translational initiation at internal codons positioned in proximity to a ribosome acceptor sequence. Sendai virus exploits shunting to express a series of proteins that initiate at the fourth and fifth start sites on the P/C mRNA (namely, the Y1 and Y2 proteins, respectively). Shunt-mediated initiation at these sites is codon independent. In an attempt to characterise the acceptor site, an extensive deletion analysis was performed spanning the entire C ORF. Only mutants flanking the Y1/Y2 start sites exhibited altered shunt phenotypes. Some of these significantly enhanced shunting efficiency to the point where the Y1/Y2 proteins were the major translational products of the mRNA. Additionally, removal of a short region just downstream of the Y2 start codon (referred to as Delta10) ablated all Y protein initiation via shunting but had no effect on Y expression when the AUG codons were viewed by a scanning ribosome. Point mutations introduced into this Delta10 sequence severely perturbed shunt-mediated initiation. We also provide evidence that changes in this region of the P/C mRNA may be used to modulate Y protein expression levels in different viral strains.
de Breyne
Sylvain
S
Department of Genetics and Microbiology, The University of Geneva Medical School (CMU), 1, rue Michel Servet, CH-1211 Geneva 4, Switzerland.
Simonet
Viviane
V
Pelet
Thierry
T
Curran
Joseph
J
D001483:Base Sequence; D018387:Codon, Initiator / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D029082:Sendai virus / Q000235:genetics*; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D014407:Tumor Cells, Cultured; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
D018387:Codon, Initiator; D004279:DNA, Viral; D014764:Viral Proteins