title: Structural comparisons of wild-type and nuclear transport-defective simian virus 40 large tumor antigens.
abstract: PARA(nT) is a defective SV40-adenovirus 7 hybrid virus which contains the entire early region of the SV40 genome and codes for the synthesis of SV40 large tumor antigen (T-ag). A transport-defective variant of this hybrid, PARA(cT), encodes T-ag that is not transported to the nucleus, but accumulates in the cytoplasm. The structures of T-ags extracted from wild-type (WT) SV40-, PARA(nT)-, and PARA(cT)-infected cells were compared by peptide mapping. All three types of T-ag underwent considerable degradation when extracted using Tris-buffered Nonidet P-40 at pH 8.0. The addition of 200 microM leupeptin to the extraction buffer significantly inhibited this degradation. Comparison of methionine-containing tryptic peptides revealed no differences among the T-ags, suggesting that their primary structures are similar or identical. Phosphopeptide mapping revealed no differences between SV40- and PARA(nT)-encoded T-ags. In contrast, PARA(cT)-encoded T-ag lacked a prominent phosphopeptide that was present in both of the others. The possible relevance of this difference in phosphorylation to the transport defect is discussed.
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000595:Amino Acid Sequence; D000957:Antigens, Viral, Tumor / Q000032:analysis* / Q000235:genetics / Q000302:isolation & purification; D001692:Biological Transport; D002467:Cell Nucleus / Q000276:immunology; D006824:Hybridization, Genetic; D007976:Leupeptins; D008715:Methionine / Q000032:analysis; D009154:Mutation; D017830:Octoxynol; D010455:Peptides / Q000032:analysis; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D011092:Polyethylene Glycols; D013539:Simian virus 40 / Q000235:genetics / Q000276:immunology*; D014764:Viral Proteins / Q000032:analysis
chemical_list: D000957:Antigens, Viral, Tumor; D007976:Leupeptins; D010455:Peptides; D010748:Phosphopeptides; D014764:Viral Proteins; D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40; D008715:Methionine; C032854:leupeptin