title: Mutation of host DnaJ homolog inhibits brome mosaic virus negative-strand RNA synthesis.
abstract: The replication of positive-strand RNA viruses involves not only viral proteins but also multiple cellular proteins and intracellular membranes. In both plant cells and the yeast Saccharomyces cerevisiae, brome mosaic virus (BMV), a member of the alphavirus-like superfamily, replicates its RNA in endoplasmic reticulum (ER)-associated complexes containing viral 1a and 2a proteins. Prior to negative-strand RNA synthesis, 1a localizes to ER membranes and recruits both positive-strand BMV RNA templates and the polymerase-like 2a protein to ER membranes. Here, we show that BMV RNA replication in S. cerevisiae is markedly inhibited by a mutation in the host YDJ1 gene, which encodes a chaperone Ydj1p related to Escherichia coli DnaJ. In the ydj1 mutant, negative-strand RNA accumulation was inhibited even though 1a protein associated with membranes and the positive-strand RNA3 replication template and 2a protein were recruited to membranes as in wild-type cells. In addition, we found that in ydj1 mutant cells but not wild-type cells, a fraction of 2a protein accumulated in a membrane-free but insoluble, rapidly sedimenting form. These and other results show that Ydj1p is involved in forming BMV replication complexes active in negative-strand RNA synthesis and suggest that a chaperone system involving Ydj1p participates in 2a protein folding or assembly into the active replication complex.
authors.affiliation: Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Tomita
authors.forename: Tomomitsu
authors.initials: T
authors.lastname: Mizuno
authors.forename: Juana
authors.initials: J
authors.lastname: Díez
authors.forename: Satoshi
authors.initials: S
authors.lastname: Naito
authors.forename: Paul
authors.initials: P
authors.lastname: Ahlquist
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ishikawa
mesh_terms: D017795:Bromovirus / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D012367:RNA, Viral / Q000096:biosynthesis*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D029701:Saccharomyces cerevisiae Proteins; D017385:Sequence Homology; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D012367:RNA, Viral; D029701:Saccharomyces cerevisiae Proteins; C070319:YDJ1 protein, S cerevisiae; D012324:RNA-Dependent RNA Polymerase