ABSTRACT
Programmed ribosomal frameshifting is used in the expression of many virus genes and some cellular genes. In eukaryotic systems, the most well-characterized mechanism involves -1 tandem tRNA slippage on an X_XXY_YYZ motif. By contrast, the mechanisms involved in programmed +1 (or -2) slippage are more varied and often poorly characterized. Recently, a novel gene, PA-X, was discovered in influenza A virus and found to be expressed via a shift to the +1 reading frame. Here, we identify, by mass spectrometric analysis, both the site (UCC_UUU_CGU) and direction (+1) of the frameshifting that is involved in PA-X expression. Related sites are identified in other virus genes that have previously been proposed to be expressed via +1 frameshifting. As these viruses infect insects (chronic bee paralysis virus), plants (fijiviruses and amalgamaviruses) and vertebrates (influenza A virus), such motifs may form a new class of +1 frameshift-inducing sequences that are active in diverse eukaryotes.
Subject(s)
Frameshifting, Ribosomal/physiology , Gene Expression Regulation, Viral/physiology , Influenza A virus/metabolism , Repressor Proteins/metabolism , Viral Nonstructural Proteins/metabolism , Influenza A virus/genetics , Repressor Proteins/genetics , Viral Nonstructural Proteins/geneticsABSTRACT
Influenza A virus (IAV) infection leads to variable and imperfectly understood pathogenicity. We report that segment 3 of the virus contains a second open reading frame ("X-ORF"), accessed via ribosomal frameshifting. The frameshift product, termed PA-X, comprises the endonuclease domain of the viral PA protein with a C-terminal domain encoded by the X-ORF and functions to repress cellular gene expression. PA-X also modulates IAV virulence in a mouse infection model, acting to decrease pathogenicity. Loss of PA-X expression leads to changes in the kinetics of the global host response, which notably includes increases in inflammatory, apoptotic, and T lymphocyte-signaling pathways. Thus, we have identified a previously unknown IAV protein that modulates the host response to infection, a finding with important implications for understanding IAV pathogenesis.
Subject(s)
Frameshifting, Ribosomal , Influenza A Virus, H1N1 Subtype/genetics , Influenza A virus/genetics , Open Reading Frames , Orthomyxoviridae Infections/virology , RNA-Dependent RNA Polymerase/genetics , RNA-Dependent RNA Polymerase/metabolism , Repressor Proteins/genetics , Repressor Proteins/metabolism , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolism , Viral Proteins/genetics , Viral Proteins/metabolism , Amino Acid Sequence , Animals , Base Sequence , Cell Line , Codon , Conserved Sequence , Female , Gene Expression Regulation , Genome, Viral , HEK293 Cells , Humans , Influenza A Virus, H1N1 Subtype/growth & development , Influenza A Virus, H1N1 Subtype/pathogenicity , Influenza A virus/metabolism , Lung/pathology , Lung/virology , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Mutation , Orthomyxoviridae Infections/genetics , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/pathology , Protein Interaction Domains and Motifs , Proteome , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Viral/genetics , RNA, Viral/metabolism , RNA-Dependent RNA Polymerase/chemistry , Reassortant Viruses/genetics , Repressor Proteins/chemistry , Viral Nonstructural Proteins/chemistry , Viral Proteins/biosynthesis , Viral Proteins/chemistry , Virus ReplicationSubject(s)
Prostatectomy/instrumentation , Surgical Instruments , Humans , Ligation/instrumentation , MaleABSTRACT
A woman is described in whom an intrauterine device eroded through the bladder wall, causing calculus formation and chronic infection.
