Showing papers by "Erich A. Nigg published in 1982"

Immunofluorescent localization of the transforming protein of Rous sarcoma virus with antibodies against a synthetic src peptide

Abstract: Antisera were raised against a synthetic peptide (src-c) containing the six COOH-terminal amino acids of p60src, the transforming protein of Rous sarcoma virus (RSV). Antibodies specific for the src-c peptide were purified by affinity chromatography and then used to study the location of p60src in transformed cells. The distribution of p60src was compared to that of vinculin, a candidate cytoskeletal substrate of p60src, by indirect double immunofluorescence microscopy. In RSV-transformed rat, mouse, and chicken cells, an extensive codistribution of p60src with vinculin was observed. Both proteins were concentrated in the few remaining focal adhesion plaques, in transformation-induced rosette clusters at the ventral cell surface, and in cell-cell contact areas. In addition, antibodies to both proteins stained the cytoplasm diffusely. In all cells examined, the immunofluorescent staining patterns produced by antibodies to the src-c peptide were indistinguishable from those obtained by immunolabeling of p60src with sera from RSV-infected tumor-bearing rabbits. The excellent agreement of the results obtained with two completely independent antibody preparations indicates strongly that the observed immunolabeling patterns correctly define the intracellular distribution of p60src. The significance of the intracellular location of p60src to the transforming activities of the protein is discussed.

On the nature of crossreactions observed with antibodies directed to defined epitopes

Abstract: Antibodies directed against a synthetic peptide (src-c) containing the six carboxyl-terminal amino acids of p60src, the transforming protein of Rous sarcoma virus, recognize p60src. However, when used at sufficiently high concentrations they also react with a number of constituents of untransformed cells. These reactions can be completely inhibited by src-c peptide. Crossreactivities are to different components in cells from different species and cannot be attributed to p60c-src, the ubiquitous cellular homologue of p60src. By indirect immunofluorescence microscopy and immunochemical techniques we have identified three cytoskeletal proteins, myosin, tubulin, and vimentin, as well as an unknown intranuclear antigen, as major targets of anti-src-c antibodies in different untransformed cells. These crossreactivities probably reflect identities or similarities in the amino acid sequence of the immunogenic peptide and segments of the otherwise unrelated crossreactive proteins. These findings are discussed with respect to the interpretation of crossreactivities that are occasionally observed with anti-peptide sera and with monoclonal antibodies.