title: Characterization of an immortalizing N-terminal domain of polyomavirus large T antigen.
abstract: Polyomavirus large T antigen has an N-terminal domain of approximately 260 amino acids which can immortalize primary cells but lacks sequences known to be required for DNA binding and replication. Treatment of full-length large T with either V8 protease or chymotrypsin yields an N-terminal fragment of 36 to 40 kDa and a C-terminal fragment of approximately 60 kDa. This finding suggests a division of the protein into two domains. Proteolysis experiments show that the N-terminal domain does not have strong physical association with the rest of the protein. It also does not self-associate. A construct expressing only the N-terminal 259 amino acids is sufficient for immortalization. The independently expressed N-terminal domain is multiply phosphorylated, although at a lower level than the same region in full-length large T. The 259-residue protein binds to both pRb and p107 with somewhat lower efficiency than the full-length protein.
authors.affiliation: Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111.
authors.forename: P S
authors.initials: PS
authors.lastname: Holman
authors.forename: O V
authors.initials: OV
authors.lastname: Gjoerup
authors.forename: T
authors.initials: T
authors.lastname: Davin
authors.forename: B S
authors.initials: BS
authors.lastname: Schaffhausen
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000235:genetics* / Q000378:metabolism; D002472:Cell Transformation, Viral / Q000235:genetics*; D002918:Chymotrypsin / Q000378:metabolism; D051379:Mice; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011120:Polyomavirus / Q000235:genetics* / Q000276:immunology*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D016160:Retinoblastoma Protein / Q000378:metabolism; D017384:Sequence Deletion; D012697:Serine Endopeptidases / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000957:Antigens, Viral, Tumor; D010446:Peptide Fragments; D016160:Retinoblastoma Protein; D012697:Serine Endopeptidases; D002918:Chymotrypsin; C028344:glutamyl endopeptidase