Hepatitis C virus internal ribosome entry site-dependent translation in Saccharomyces cerevisiae is independent of polypyrimidine tract-binding protein, poly(rC)-binding protein 2, and La protein.
Translation initiation of some viral and cellular mRNAs occurs by ribosome binding to an internal ribosome entry site (IRES). Internal initiation mediated by the hepatitis C virus (HCV) IRES in Saccharomyces cerevisiae was shown by translation of the second open reading frame in a bicistronic mRNA. Introduction of a single base change in the HCV IRES, known to abrogate internal initiation in mammalian cells, abolished translation of the second open reading frame. Internal initiation mediated by the HCV IRES was independent of the nonsense-mediated decay pathway and the cap binding protein eIF4E, indicating that translation is not a result of mRNA degradation or 5'-end-dependent initiation. Human La protein binds the HCV IRES and is required for efficient internal initiation. Disruption of the S. cerevisiae genes that encode La protein orthologs and synthesis of wild-type human La protein in yeast had no effect on HCV IRES-dependent translation. Polypyrimidine tract-binding protein (Ptb) and poly-(rC)-binding protein 2 (Pcbp2), which may be required for HCV IRES-dependent initiation in mammalian cells, are not encoded within the S. cerevisiae genome. HCV IRES-dependent translation in S. cerevisiae was independent of human Pcbp2 protein and stimulated by the presence of human Ptb protein. These findings demonstrate that the genome of S. cerevisiae encodes all proteins necessary for internal initiation of translation mediated by the HCV IRES.
Rosenfeld
Amy B
AB
Department of Microbiology, Columbia University College of Physicians & Surgeons, 701 W. 168th St., New York, New York 10032, USA.
Racaniello
Vincent R
VR
D001324:Autoantigens / Q000502:physiology*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D016174:Hepacivirus / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D038941:Polypyrimidine Tract-Binding Protein / Q000502:physiology*; D014176:Protein Biosynthesis; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000502:physiology*; D012261:Ribonucleoproteins / Q000502:physiology*; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*; D000097585:SS-B Antigen
D001324:Autoantigens; D004268:DNA-Binding Proteins; D038941:Polypyrimidine Tract-Binding Protein; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D014157:Transcription Factors; D000097585:SS-B Antigen; C501903:PCBP2 protein, human