title: A subclass of polyomavirus middle tumor antigen binds to DNA cellulose.
abstract: We examined the binding of polyomavirus large (L-T)-, middle (M-T)-, and small-tumor antigens to DNA cellulose. At pH 6.0, the majority of L-T bound to calf thymus DNA cellulose, while little or no small tumor antigen was retained under these conditions. Unexpectedly, a small but reproducible proportion of M-T bound to both native and denatured DNA cellulose. M-T encoded by polyomavirus mutant dl 8, which expressed shortened L-T and M-T, bound to DNA, indicating that the deleted sequences are not required for DNA binding. Also, M-T from transformed BMT-1 rat cells, which synthesize exclusively this polyomavirus tumor antigen, bound to DNA, indicating that its binding is not due to association with other polyomavirus-encoded proteins. Using the DNA fragment immunoassay, we found that, under conditions in which L-T bound specifically to DNA fragments containing viral regulatory sequences, no viral DNA fragments were bound by M-T. The existence of distinct subpopulations of M-T that differ in their DNA-binding properties was indicated by rebinding experiments in which M-T that had bound to DNA cellulose rebound very efficiently, while that which had not been originally retained by DNA cellulose rebound poorly. Furthermore, the M-T-pp60 c-src complex did not bind to DNA cellulose. These data suggest that polyomavirus M-T is heterogeneous, consisting of populations of molecules that differ in their interactions with DNA cellulose.
mesh_terms: D000957:Antigens, Viral, Tumor / Q000145:classification; D002846:Chromatography, Affinity; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005814:Genes, Viral; D008970:Molecular Weight; D009154:Mutation; D011120:Polyomavirus / Q000235:genetics* / Q000276:immunology; D011494:Protein Kinases / Q000378:metabolism
chemical_list: D000957:Antigens, Viral, Tumor; D004268:DNA-Binding Proteins; D004247:DNA; D011494:Protein Kinases