Poorly expressed endogenous ecotropic provirus of DBA/2 mice encodes a mutant Pr65gag protein that is not myristylated.
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.
Copeland
N G
NG
Bionetics Research, Inc., National Cancer Institute, Frederick, Maryland 21701.
Jenkins
N A
NA
Nexø
B
B
Schultz
A M
AM
Rein
A
A
Mikkelsen
T
T
Jørgensen
P
P
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
D004279:DNA, Viral; D015683:Gene Products, gag; D009227:Myristic Acids; D012191:Retroviridae Proteins; D004262:DNA Restriction Enzymes