title: The small envelope protein E is not essential for murine coronavirus replication.
abstract: The importance of the small envelope (E) protein in the assembly of coronaviruses has been demonstrated in several studies. While its precise function is not clearly defined, E is a pivotal player in the morphogenesis of the virion envelope. Expression of the E protein alone results in its incorporation into vesicles that are released from cells, and the coexpression of the E protein with the membrane protein M leads to the assembly of coronavirus-like particles. We have previously generated E gene mutants of mouse hepatitis virus (MHV) that had marked defects in viral growth and produced virions that were aberrantly assembled in comparison to wild-type virions. We have now been able to obtain a viable MHV mutant in which the entire E gene, as well as the nonessential upstream genes 4 and 5a, has been deleted. This mutant (Delta E) was obtained by a targeted RNA recombination method that makes use of a powerful host range-based selection system. The Delta E mutant produces tiny plaques with an unusual morphology compared to plaques formed by wild-type MHV. Despite its low growth rate and low infectious titer, the Delta E mutant is genetically stable, showing no detectable phenotypic changes after several passages. The properties of this mutant provide further support for the importance of E protein in MHV replication, but surprisingly, they also show that E protein is not essential.
authors.affiliation: Wadsworth Center, New York State Department of Health, Albany, New York 12201, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Kuo
authors.forename: Paul S
authors.initials: PS
authors.lastname: Masters
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017353:Gene Deletion; D051379:Mice; D006517:Murine hepatitis virus / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D012367:RNA, Viral / Q000235:genetics; D011995:Recombination, Genetic; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*; D010948:Viral Plaque Assay; D014779:Virus Replication
chemical_list: D012367:RNA, Viral; D014759:Viral Envelope Proteins