Characterization of polyoma mutants with altered middle and large T-antigens

Magnusson, Göran; Nilsson, Maj-Greth; Dilworth, S. J.; Smolar, Nina

doi:10.1128/jvi.39.3.673-683.1981

Cited by 50 publications

(23 citation statements)

References 38 publications

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“…1178T (31) shows dramatically reduced binding of PI 3-kinase, while Y250F (8, 9, 32) is deficient in associating with SHC and thereby unable to initiate signaling through Ras. NG59 (38) binds none of the molecules characterized so far, 1387T (a truncated mutant protein lacking the membrane anchor sequence) only binds PP2A (39,60), and dl1015 associates with all cellular enzymes described so far, but is unable to activate PI 3-kinase (40,41). Mutant genes were introduced into NIH 3T3 cells and activation of MAP kinase measured in the luciferase reporter assay.…”

Section: Polyomavirus Middle-t Activates Map Kinases-middle-tmentioning

confidence: 99%

Activation and Nuclear Translocation of Mitogen-activated Protein Kinases by Polyomavirus Middle-T or Serum Depend on Phosphatidylinositol 3-Kinase

Urich¹,

Shemerly

Besser³

et al. 1995

Journal of Biological Chemistry

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Several cellular signal transduction pathways activated by middle-T in polyomavirus-transformed cells are required for viral oncogenicity. Here we focus on the role of phosphatidylinositol 3-kinase (PI 3-kinase) and Ras and address the question how these signaling molecules cooperate during cell cycle activation. Ras activation is mediated through association with SHC.GRB2.SOS and leads to increased activity of several members of the mitogen-activated protein (MAP) kinase family, while activation of PI 3-kinase results in the generation of D3-phosphorylated phosphatidylinositides whose downstream targets remain elusive. PI 3-kinase activation might also ensue as a direct consequence of Ras activation. Oncogenicity of middle-T requires stimulation of both Ras- and PI 3-kinase-dependent pathways. Mutants of middle-T incapable to bind either SHC.GRB2.SOS or PI 3-kinase are not oncogenic. Sustained activation and nuclear localization of one of the MAP kinases, ERK1, was observed in wild type but not in mutant middle-T-expressing cells. Wortmannin, an inhibitor of PI 3-kinase, prevented MAP kinase activation and nuclear localization in middle-T-transformed cells. PI 3-kinase activity was also required for activation of the MAP kinase pathway in normal serum-stimulated cells, generalizing the concept that signaling through MAP kinases requires not only Ras-but also PI 3-kinase-mediated signals.

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Section: Polyomavirus Middle-t Activates Map Kinases-middle-tmentioning

confidence: 99%

Activation and Nuclear Translocation of Mitogen-activated Protein Kinases by Polyomavirus Middle-T or Serum Depend on Phosphatidylinositol 3-Kinase

Urich¹,

Shemerly

Besser³

et al. 1995

Journal of Biological Chemistry

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“…contains most of the postulated amino acid changes in middle T-antigen as well as two large T-antigen changes. Some segments of this region can be deleted from the polyoma genome without greatly affecting viral DNA replication or cellular transformation, functions ascribed to large T-antigen and middle T-antigen, respectively (2,18,31,32). However, at least one sequence including four consecutive glutamic acid residues and a tyrosine residue is crucial for transformation (18,35).…”

Section: -* Asp and Ile-289 -* Thr Substitutionsmentioning

confidence: 99%

Comparison of the DNA sequence of the Crawford small-plaque variant of polyomavirus with those of polyomaviruses A2 and strain 3

Rothwell¹,

Folk²

1983

J Virol

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The DNA sequence of two wild-type strains of polyomavirus (A2 and strain 3) are known. We have determined the majority of the DNA sequence of a third strain, the Crawford small-plaque virus. This virus has been noted for its capacity to induce readily detected tumor-specific transplantation antigen in hamster cells, a property that is most likely attributable to an altered middle T-antigen. A comparison of its DNA sequence with those of the A2 and strain 3 viruses reveals numerous nucleotide substitutions, insertions, and deletions throughout the genome. Most sequence changes in coding regions are silent mutations; however, variability in proteins can be predicted from these sequence data at 5 locations in middle T-antigen, 10 in large T-antigen, and 10 in VP1. The Crawford small-plaque virus noncoding regulatory region contains, in addition to nucleotide substitutions, a 44-base-pair tandem repeat of sequences on the late side of the origin of DNA replication.

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“…d145 is a wild-type deletion strain isolated by Bendig and colleagues (1). d18 (9) and d11015 (15,16) are deletion mutants for which the large T-antigen function may be affected, as judged by the growth properties of the virus. dl23 (9) is a deletion mutant that is transformation defective as a result of its middle T antigen defect, but its large T antigen appears unaffected by the mutation.…”

Section: Methodsmentioning

confidence: 99%

Localization of the phosphorylations of polyomavirus large T antigen

Bockus¹,

Schaffhausen²

1987

J Virol

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Polyomavirus large T antigen is phosphorylated on both serine and threonine residues at a ratio of approximately 6 to 1. This phosphorylation could be resolved into a series of nine Staphylococcus aureus V8 phosphopeptides. All of these were found in an N-terminal chymotryptic fragment with a molecular weight of 57,000. A C-terminal formic acid fragment of 50,000-molecular-weight lacked phosphate. Therefore, unlike simian virus 40 large T antigen, polyomavirus large T antigen has no significant C-terminal phosphorylation. Limited V8 and hydroxylamine cleavage showed that the phosphorylations can be localized to two different portions of the molecule. A significant fraction of the phosphate was localized in the N-terminal portion of the molecule before residue 183. Within this region V8 peptides 4, 8, and 9 represented phosphorylations that were more proximal, while peptides 1, 2, and 3 included more distal phosphorylations. None of these phosphorylations appeared analogous to those of simian virus 40 large T antigen. V8 phosphopeptides 5 and 7 were more distal and could be distinguished in biological experiments from the N-terminal phosphorylations. Formic acid mapping suggested that much, if not all, of this phosphorylation is located between residues 257 and 285.

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Characterization of polyoma mutants with altered middle and large T-antigens

Cited by 50 publications

References 38 publications

Activation and Nuclear Translocation of Mitogen-activated Protein Kinases by Polyomavirus Middle-T or Serum Depend on Phosphatidylinositol 3-Kinase

Activation and Nuclear Translocation of Mitogen-activated Protein Kinases by Polyomavirus Middle-T or Serum Depend on Phosphatidylinositol 3-Kinase

Comparison of the DNA sequence of the Crawford small-plaque variant of polyomavirus with those of polyomaviruses A2 and strain 3

Localization of the phosphorylations of polyomavirus large T antigen

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