title: Myxoma virus M-T5 protects infected cells from the stress of cell cycle arrest through its interaction with host cell cullin-1.
abstract: The myxoma virus (MV) M-T5 gene encodes an ankyrin repeat protein that is important for virus replication in cells from several species. Insight was gained into the molecular mechanisms underlying the role of M-T5 as a host range determinant when the cell cycle regulatory protein cullin-1 (cul-1) was identified as a cellular binding partner of M-T5 and found to colocalize with the protein in both nuclear and cytosolic compartments. Consistent with this interaction, infection with wild-type MV (vMyxlac) or a deletion mutant lacking M-T5 (vMyxT5KO) differentially altered cell cycle progression in a panel of permissive and nonpermissive cells. Cells infected with vMyxlac transitioned rapidly out of the G0/G1 phase and preferentially accumulated at the G2/M checkpoint, whereas infection with vMyxT5KO impeded progression through the cell cycle, resulting in a greater percentage of cells retained at G0/G1. Levels of the cul-1 substrate, p27/Kip-1, were selectively increased in cells infected with vMyxT5KO compared to vMyxlac, concurrent with decreased phosphorylation of p27/Kip-1 at Thr187 and decreased ubiquitination. Compared to cells infected with vMyxlac, cell death was increased in vMyxT5KO-infected cells following treatment with diverse stimuli known to induce cell cycle arrest, including infection itself, serum deprivation, and exposure to proteasome inhibitors or double-stranded RNA. Moreover, infection with vMyxlac, but not vMyxT5KO, was sufficient to overcome the G0/G1 arrest induced by these stimuli. These findings suggest that M-T5 regulates cell cycle progression at the G0/G1 checkpoint, thereby protecting infected cells from diverse innate host antiviral responses normally triggered by G0/G1 cell cycle arrest.
authors.affiliation: BioTherapeutics Research Group, Robarts Research Institute, SDRI Rm. 133, 1400 Western Road, London, Ontario N6G 2V4, Canada.
authors.forename: J B
authors.initials: JB
authors.lastname: Johnston
authors.forename: G
authors.initials: G
authors.lastname: Wang
authors.forename: J W
authors.initials: JW
authors.lastname: Barrett
authors.forename: S H
authors.initials: SH
authors.lastname: Nazarian
authors.forename: K
authors.initials: K
authors.lastname: Colwill
authors.forename: M
authors.initials: M
authors.lastname: Moran
authors.forename: G
authors.initials: G
authors.lastname: McFadden
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D044842:Cullin Proteins / Q000502:physiology*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D006801:Humans; D008969:Molecular Sequence Data; D009233:Myxoma virus / Q000502:physiology*; D010766:Phosphorylation; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000502:physiology*
chemical_list: D018797:Cell Cycle Proteins; C100318:Cullin 1; D044842:Cullin Proteins; C100338:M-T5 protein, Myxoma virus; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D014764:Viral Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27