title: Poorly expressed endogenous ecotropic provirus of DBA/2 mice encodes a mutant Pr65gag protein that is not myristylated.
abstract: DBA/2 mice carry a single endogenous ecotropic murine leukemia provirus designated Emv-3. Although this provirus appears to be nondefective by genomic restriction enzyme mapping, weanling mice do not produce virus and only about one-third of adult mice ever express virus. 5-Iododeoxyuridine and 5-azacytidine, two potent inducers of ecotropic virus expression, are relatively ineffective at inducing Emv-3 expression. However, the chemical carcinogen 7,12-dimethylbenz(a)anthracene can induce ecotropic virus expression in approximately 95% of treated DBA/2 mice. Previous experiments involving DNA transfection and marker rescue analysis of molecularly cloned Emv-3 DNA suggested that Emv-3 carries a small defect(s) in the gag gene, not detectable by restriction enzyme mapping, that inhibits virus expression in vivo and in vitro. Using a combination of approaches, including DNA sequencing, peptide mapping, and metabolic labeling of cells with [3H]myristate, we have demonstrated that the defect in Emv-3 most likely results from a single nucleotide substitution within the gene for p15gag that inhibits myristylation of the Pr65gag N terminus. Myristylation of Pr65gag is thought to be required for this protein to associate with the plasma membrane and is essential for virus particle formation. These results provide a conceptual framework for understanding how Emv-3 expression is regulated during development and after chemical induction.
authors.affiliation: Bionetics Research, Inc., National Cancer Institute, Frederick, Maryland 21701.
authors.forename: N G
authors.initials: NG
authors.lastname: Copeland
authors.forename: N A
authors.initials: NA
authors.lastname: Jenkins
authors.forename: B
authors.initials: B
authors.lastname: Nexø
authors.forename: A M
authors.initials: AM
authors.lastname: Schultz
authors.forename: A
authors.initials: A
authors.lastname: Rein
authors.forename: T
authors.initials: T
authors.lastname: Mikkelsen
authors.forename: P
authors.initials: P
authors.lastname: Jørgensen
mesh_terms: D000818:Animals; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004279:DNA, Viral / Q000235:genetics; D005786:Gene Expression Regulation; D015683:Gene Products, gag; D005814:Genes, Viral; D009052:Leukemia Virus, Murine / Q000235:genetics*; D051379:Mice; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D009154:Mutation; D009227:Myristic Acids / Q000378:metabolism; D010449:Peptide Mapping; D011533:Proviruses / Q000235:genetics*; D012191:Retroviridae Proteins / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D015683:Gene Products, gag; D009227:Myristic Acids; D012191:Retroviridae Proteins; D004262:DNA Restriction Enzymes