Open AccessA mutant allele of essential, general translation initiation factor DED1 selectively inhibits translation of a viral mRNA
Author(s) -
Amine Noueiry,
Jianbo Chen,
Paul Ahlquist
Publication year - 2000
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.240460897
Subject(s) - biology , translation (biology) , rna , mutant , rna helicase a , messenger rna , brome mosaic virus , genetics , gene , microbiology and biotechnology , rna dependent rna polymerase , helicase
Positive-strand RNA virus genomes are substrates for translation, RNA replication, and encapsidation. To identify host factors involved in these functions, we used the ability of brome mosaic virus (BMV) RNA to replicate in yeast. We report herein identification of a mutation in the essential yeast geneDED1 that inhibited BMV RNA replication but not yeast growth.DED1 encodes a DEAD (Asp-Glu-Ala-Asp)-box RNA helicase required for translation initiation of all yeast mRNAs. Inhibition of BMV RNA replication by the mutantDED1 allele (ded1–18 ) resulted from inhibited expression of viral polymerase-like protein 2a, encoded by BMV RNA2. Inhibition of RNA2 translation was selective, with no effect on general cellular translation or translation of BMV RNA1-encoded replication factor 1a, and was independent of p20, a cellular antagonist ofDED1 function in translation. Inhibition of RNA2 translation inded1–18 yeast required the RNA2 5′ noncoding region (NCR), which also conferred aded1–18 -specific reduction in expression on a reporter gene mRNA. Comparison of the similar RNA1 and RNA2 5′ NCRs identified a 31-nucleotide RNA2-specific region that was required for theded1–18 -specific RNA2 translation block and attenuated RNA2 translation in wild-type yeast. Further comparisons and RNA structure predictions suggest a modular arrangement of replication and translation signals in RNA1 and RNA2 5′ NCRs that appears conserved among bromoviruses. The 5′ attenuator andDED1 dependence of RNA2 suggest that, despite its divided genome, BMV regulates polymerase translation relative to other replication factors, just as many single-component RNA viruses use translational read-through and frameshift mechanisms to down-regulate polymerase. The results show that a DEAD-box helicase can selectively activate translation of a specific mRNA and may provide a paradigm for translational regulation by other members of the ubiquitous DEAD-box RNA helicase family.