title: Analysis of mutations within the cytoplasmic domain of the Moloney murine leukemia virus transmembrane protein.
abstract: The role of the cytoplasmic tail of the Moloney murine leukemia virus transmembrane protein in the regulation of syncytia was examined. Three mutations within the cytoplasmic tail were studied. Linker-insertion in7705-12a is within the viral-associated cytoplasmic tail, linker-insertion in7748-12a is within the R peptide, and a third mutation expresses TM lacking the R peptide (Env R-). The Env R- construct was nonviable in Rat1 cells, however, rapidly reverted to a form containing the R peptide when passaged in NIH/3T3 cells. in7705-12a was temperature-sensitive in Rat1 cells, as previously characterized, but was viable at either temperature in NIH/3T3 cells. in7748-12a was comparable with wild-type M-MuLV. The ability of the env constructs to form large multinucleated syncytia with NIH/3T3 and XC cells were examined using transient expression assays, eliminating reversion events due to viral passage and reverse transcription. The Env R- constructs formed syncytia with NIH/3T3 cells. in7705-12a displays enhanced proteolytic cleavage of the R peptide. Neither linker-insertion mutation in7705-12a or in7748-12a activated fusion with NIH/3T3, despite the abundance of processed TM with in7705-12a. All three mutants were fusion competent with Rat XC cells, even in the absence of any cleavage of the R peptide. These results provide insights regarding steric and the temporal affects of cleavage of the R peptide and the assembly of a fusion competent oligomer.
authors.affiliation: Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854, USA.
authors.forename: A
authors.initials: A
authors.lastname: Thomas
authors.forename: K D
authors.initials: KD
authors.lastname: Gray
authors.forename: M J
authors.initials: MJ
authors.lastname: Roth
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D017931:DNA Primers; D017353:Gene Deletion; D015752:Genes, env; D015726:Giant Cells; D006801:Humans; D051379:Mice; D008979:Moloney murine leukemia virus / Q000235:genetics* / Q000502:physiology; D016254:Mutagenesis, Insertional; D016133:Polymerase Chain Reaction; D011533:Proviruses / Q000235:genetics / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D015682:Retroviridae Proteins, Oncogenic / Q000096:biosynthesis / Q000235:genetics*; D014759:Viral Envelope Proteins / Q000096:biosynthesis / Q000235:genetics*; D014764:Viral Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D014779:Virus Replication
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D015682:Retroviridae Proteins, Oncogenic; D014759:Viral Envelope Proteins; D014764:Viral Proteins; C078678:p15E protein, Murine leukemia virus