title: Dominant negative mutants of the murine cytomegalovirus M53 gene block nuclear egress and inhibit capsid maturation.
abstract: The alphaherpesvirus proteins UL31 and UL34 and their homologues in other herpesvirus subfamilies cooperate at the nuclear membrane in the export of nascent herpesvirus capsids. We studied the respective betaherpesvirus proteins M53 and M50 in mouse cytomegalovirus (MCMV). Recently, we established a random approach to identify dominant negative (DN) mutants of essential viral genes and isolated DN mutants of M50 (B. Rupp, Z. Ruzsics, C. Buser, B. Adler, P. Walther and U. H. Koszinowski, J. Virol 81:5508-5517). Here, we report the identification and phenotypic characterization of DN alleles of its partner, M53. While mutations in the middle of the M53 open reading frame (ORF) resulted in DN mutants inhibiting MCMV replication by approximately 100-fold, mutations at the C terminus resulted in up to 1,000,000-fold inhibition of virus production. C-terminal DN mutants affected nuclear distribution and steady-state levels of the nuclear egress complex and completely blocked export of viral capsids. In addition, they induced a marked maturation defect of viral capsids, resulting in the accumulation of nuclear capsids with aberrant morphology. This was associated with a two-thirds reduction in the total amount of unit length genomes, indicating an accessory role for M53 in DNA packaging.
authors.affiliation: Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität München, Genzentrum, Feodor Lynen Str. 25, 81377 Munich, Germany.
authors.forename: Mirela
authors.initials: M
authors.lastname: Popa
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Ruzsics
authors.forename: Mark
authors.initials: M
authors.lastname: Lötzerich
authors.forename: Lars
authors.initials: L
authors.lastname: Dölken
authors.forename: Christopher
authors.initials: C
authors.lastname: Buser
authors.forename: Paul
authors.initials: P
authors.lastname: Walther
authors.forename: Ulrich H
authors.initials: UH
authors.lastname: Koszinowski
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins / Q000378:metabolism; D002478:Cells, Cultured; D051379:Mice; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D018146:Muromegalovirus / Q000235:genetics / Q000502:physiology*; D020125:Mutation, Missense; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins; D014764:Viral Proteins