Format

Send to

Choose Destination
Nucleic Acids Res. 2011 Sep 1;39(17):7775-90. doi: 10.1093/nar/gkr487. Epub 2011 Jun 21.

Overlapping signals for translational regulation and packaging of influenza A virus segment 2.

Author information

1
Department of Pathology, University of Cambridge, CB2 1QP, UK.

Abstract

Influenza A virus segment 2 mRNA expresses three polypeptides: PB1, PB1-F2 and PB1-N40, from AUGs 1, 4 and 5 respectively. Two short open reading frames (sORFs) initiated by AUGs 2 and 3 are also present. To understand translational regulation in this system, we systematically mutated AUGs 1-4 and monitored polypeptide synthesis from plasmids and recombinant viruses. This identified sORF2 as a key regulatory element with opposing effects on PB1-F2 and PB1-N40 expression. We propose a model in which AUGs 1-4 are accessed by leaky ribosomal scanning, with sORF2 repressing synthesis of downstream PB1-F2. However, sORF2 also up-regulates PB1-N40 expression, most likely by a reinitiation mechanism that permits skipping of AUG4. Surprisingly, we also found that in contrast to plasmid-driven expression, viruses with improved AUG1 initiation contexts produced less PB1 in infected cells and replicated poorly, producing virions with elevated particle:PFU ratios. Analysis of the genome content of virus particles showed reduced packaging of the mutant segment 2 vRNAs. Overall, we conclude that segment 2 mRNA translation is regulated by a combination of leaky ribosomal scanning and reinitiation, and that the sequences surrounding the PB1 AUG codon are multifunctional, containing overlapping signals for translation initiation and for segment-specific packaging.

PMID:
21693560
PMCID:
PMC3177217
DOI:
10.1093/nar/gkr487
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Silverchair Information Systems Icon for PubMed Central
Loading ...
Support Center