Differences in biological activity and structural protein VP1 phosphorylation of polyomavirus progeny resulting from infection of primary mouse kidney and primary mouse embryo cell cultures

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mentioning

confidence: 97%

Mutations in the putative calcium-binding domain of polyomavirus VP1 affect capsid assembly

Haynes

Chang

Consigli

1993

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“…However, capsids (containing VP2 and VP3) are unable to inhibit infection by virions (7), suggesting that specific VP1 phosphorylation sites may play a role in cell recognition. This hypothesis is supported by the location of the identified phosphorylation sites in the virion structure and previous data suggesting that virions with distinct isoelectric focusing phosphorylation patterns generated by infection of different mouse cell types have different efficiencies of in vitro infectivity (25). Studies with the T-156 and T-63 mutant viruses concerning the properties of in vitro and in vivo infectivity are now in progress to determine the relationship of these functions to VPI phosphorylation.…”

Section: Discussionmentioning

confidence: 56%

Identification of the threonine phosphorylation sites on the polyomavirus major capsid protein VP1: relationship to the activity of middle T antigen

Garcea

1994

Phosphorylation of the polyomavirus major capsid protein VP1 was examined after in vivo 32p labeling of virus-infected cells. Two phosphorylated peptide fragments of VP1 were identified by protease digestion, high-performance liquid chromatography purification, mass spectrometry, and N-terminal sequencing. The peptides from residues 58 to 78 and residues 153 to 173 were phosphorylated on threonine. Site-directed mutations were introduced at these threonine sites, and mutant viruses were reconstructed. A threonine-toglycine change at residue 63 (mutant G63) and a threonine-to-alanine change at residue 156 (mutant A156) resulted in viruses defective in phosphorylation of the respective peptides after in vivo labeling. Growth of the mutant G63 virus was similar to that of the wild-type virus, but the mutant A156 was inefficient in assembly of 240S viral particles. Polyomavirus nontransforming host range (hr-t) mutants are defective in VP1 threonine phosphorylation when grown in nonpermissive cells (R. L. Garcea, K. Ballmer-Hofer, and T. L. Benjamin, J. Virol. 54:311-316, 1985). Proteolytic mapping of VP1 peptides after in vivo labeling from hr-t mutant virus infections demonstrated that both residues T-63 and T-156 were affected. These results suggest that the block in virion assembly in hr-t mutant viruses is associated with a defect in phosphorylation of threonine 156.

“…late structural proteins), polyomavirus is able to expand its functional capabilities by utilizing post-translationally modified versions of its structural proteins (e.g., VP1) for various required functions (e.g., cellular attachment and hemagglutination) (2,3). It is important to note that the enzymes responsible for these modifications are a property of the host cell (25). Polyomavirus VP1 has been demonstrated to separate into six distinct species, A (most basic) through F (most acidic), based on their isoelectric points (3).…”

Section: S -mentioning

confidence: 99%

Synthesis, posttranslational modifications, and nuclear transport of polyomavirus major capsid protein VP1

Fattaey

Consigli

1989

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Polyomavirus major capsid protein VP1 synthesis was studied in infected primary baby mouse kidney cells. A standard curve of VP1 protein was used to quantitate VP1 in the cytoplasm and nucleus of infected cells during the time course of infection. Polyomavirus VP1 continued to be accumulated in the cytoplasm of the cells until 27 h postinfection, at which time the synthesis of VP1 leveled off. VP1 continued to accumulate in the nucleus of the infected cells throughout the course of infection. The presence of the six isospecies, A to F, of polyomavirus VP1 was also studied to determine the relative quantity of each species during the time course of infection. All six species were found in the cytoplasm and nucleus of infected cells at various times postinfection. However, the relative quantity of each species was different at early as compared with later times of infection. In addition, phosphorylated VP1 was found in isolated polyribosomes of infected cells, suggesting that phosphorylation of VP1 is a cotranslational modification. Examination of the effect of macromolecular synthesis on the transport of VP1 into the nucleus of infected baby mouse kidney cells as well as the rate of its nuclear accumulation during and after protein synthesis inhibition revealed that the continual transport and accumulation of VP1 in the nucleus required protein synthesis.