Host Cell-Modified T-Antigen in Membranes of Simian Virus 40-Transformed Hamster Cells

• Published in: JNCI : Journal of the National Cancer Institute 1980-09, Vol.65 (3), p.585-593
• Main Authors: Schmidt-Ullrich, Rupert, Kahn, Stuart J., Thompson, W. Scott, Wallach, Donald F. H.
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Viral - analysis; Cell Transformation, Viral; Cells, Cultured; Cricetinae; Immunoelectrophoresis; Isoelectric Focusing; Membrane Proteins - analysis; Mice; Simian virus 40 - immunology
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/65.3.585

Highly purified plasma membranes of simian virus 40 (SV40)-transformed hamster and mouse cells were subjected to indirect immunoprecipitation and bidimensional isoelectric focusing-immunoelectrophoresis with high-titer (≥512) sera against SV40 T-antigen. An SV40-specific protein of approximately 100,000 daltons and pH-4.7 isoelectric point cross-reacted immunologically with T-antigen, which indicated the presence of a T-antigen species. However, this protein appeared to be host cell modified because of its low isoelectric point and its reactivity with heterologous antisera containing antibodies specific for neuraminidase- and trypsin-sensitive carbohydrate and/or peptide moieties lacking nuclear T-antigen. Another protein specific for the membranes of SV40-transformed cells had a molecular mass near 60,000 daltons and an isoelectric point at pH 4.5 and appeared closely associated with membrane T-antigen. It copre-cipitated with membrane T-antigen upon indirect immunoprecipitation with anti-T serum. However, when this protein was dissociated from membrane T-antigen by isoelectric focusing in the presence of Triton X-100 and urea, its reactivity with anti-T serum was lost. This suggested that the protein was not encoded in the SV40 genome.