title: Determinants for membrane association of the hepatitis C virus RNA-dependent RNA polymerase.
abstract: The hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), represented by nonstructural protein 5B (NS5B), is believed to form a membrane-associated RNA replication complex together with other nonstructural proteins and as yet unidentified host components. However, the determinants for membrane association of this essential viral enzyme have not been defined. By double label immunofluorescence analyses, NS5B was found in the endoplasmic reticulum (ER) or an ER-like modified compartment both when expressed alone or in the context of the entire HCV polyprotein. The carboxyl-terminal 21 amino acid residues were necessary and sufficient to target NS5B or a heterologous protein to the cytosolic side of the ER membrane. This hydrophobic domain is highly conserved among 269 HCV isolates analyzed and predicted to form a transmembrane alpha-helix. Association of NS5B with the ER membrane occurred by a posttranslational mechanism that was ATP-independent. These features define the HCV RdRp as a new member of the tail-anchored protein family, a class of integral membrane proteins that are membrane-targeted posttranslationally via a carboxyl-terminal insertion sequence. Formation of the HCV replication complex, therefore, involves specific determinants for membrane association that represent potential targets for antiviral intervention.
authors.affiliation: Department of Medicine II, University of Freiburg, D-79106 Freiburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Schmidt-Mende
authors.forename: E
authors.initials: E
authors.lastname: Bieck
authors.forename: T
authors.initials: T
authors.lastname: Hugle
authors.forename: F
authors.initials: F
authors.lastname: Penin
authors.forename: C M
authors.initials: CM
authors.lastname: Rice
authors.forename: H E
authors.initials: HE
authors.lastname: Blum
authors.forename: D
authors.initials: D
authors.lastname: Moradpour
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D017931:DNA Primers; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D016174:Hepacivirus / Q000201:enzymology*; D006801:Humans; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013752:Tetracycline / Q000494:pharmacology; D014158:Transcription, Genetic; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D017931:DNA Primers; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase; D013752:Tetracycline