A nucleotide substitution in the gag N terminus of the endogenous ecotropic DBA/2 virus prevents Pr65gag myristylation and virus replication

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  • Institute of Environmental and Occupational Medicine
  • Department of Molecular Biology
The endogenous ecotropic provirus Emv-3 present in DBA/2 mice is poorly expressed in the animal, as well as in cell cultures. Transfection of proviral DNA into NIH 3T3 cells localized the expression defect to the 5' region of the viral genome, spanning the untranslated region and the N-terminal part of the gag gene. Comparison of the nucleotide sequence of the Emv-3 provirus with the sequence of the highly infectious Akv murine leukemia virus revealed three nucleotide differences within the gag coding region. One of these differences was found in codon 3 of the gag polyprotein, where a Gln codon is seen in Akv and a Pro codon is differences was found in codon 3 of the gag polyprotein, where a Gln codon is seen in Akv and a Pro codon is seen in Emv-3. By site-directed mutagenesis, we showed that the defect of Emv-3 expression indeed is localized to codon 3 of the gag gene. The gag polyprotein of mammalian type C retrovirus contains myristic acid covalently linked to the N-terminal glycine. This myristylation is not seen in the Emv-3-coded gag polyprotein. We showed that the in vitro-mutagenized Emv-3 genome containing a Gln codon at position 3 of the gag gene yields a myristylated gag polyprotein. Thus, it seems most likely that the defect of expression of the Emv-3 provirus is due to the presence of a proline is position 3 of the gag polyprotein, preventing the myristylation.
Original languageEnglish
JournalJournal of Virology
Volume62
Issue9
Pages (from-to)3217-23
Number of pages6
ISSN0022-538X
Publication statusPublished - 1988

    Research areas

  • Animals, Codon, DNA Restriction Enzymes, Electrophoresis, Polyacrylamide Gel, Gene Products, gag, Genes, Viral, Leukemia Virus, Murine, Mice, Mutation, Myristates, Nucleotides, Plasmids, Proviruses, Retroviridae Proteins, Transfection, Virus Replication

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