Tumor antigen(s) in cells productively infected by wild-type polyoma virus and mutant NG-18

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Abstract
When isolated by an anti-polyoma tumor (T) antiserum, the major product from primary baby mouse kidney cells productively infected by wild-type poloma virus is a polypeptide of 100,000 apparent MW as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis [SDS/PAGE]. In cells infected by NG-18, an hr-t mutant carrying a deletion of about 150 base pairs in the early region of the viral DNA, a T antigen species appears that comigrates with that of the wild-type virus. Comparisons of peptides after partial proteolysis reveal no differences between mutant and wild-type products. Both wild-type and mutant 100,000 products can be labeled in vivo with [32P]orthophosphate. An independent and more reliable estimate of the MW of this protein using guanidine/Sepharose chromatography yields a value of 81,000 for both mutant and wild-type species. The apparent identity of wild-type and mutant products indicates that the deletion in NG-18 lies outside of the region encoding this major T antigen species. Immunoprecipitates from wild-type infected cells show 4 bands besides the 100,000 band; these have apparent MW of 63,000, 56,000, 36,000 and 22,000 by sodium dodecyl sulfate/polyacrylamide gel electrophoresis; the 56,000 and 36,000 species are phosphorylated. All 4 of these lower MW bands are absent or drastically reduced in the immunoprecipitates from NG-18-infected cells.