Association of simian virus 40 T antigen with the nuclear matrix of infected and transformed monkey cells.
The subnuclear distribution of simian virus 40 large T antigen within nuclei of transformed Cos and C6 monkey cells was examined. Cos cells express wild-type T antigen but lack viral sequences required for DNA replication, whereas C6 cells contain a functional viral origin but express a replication-defective mutant T antigen which is unable to bind specifically to viral DNA. Discrete subpopulations of T antigen were isolated from the soluble nucleoplasm, chromatin, and nuclear matrix of both cell lines. Although only a small quantity (2 to 12%) of the total nuclear T antigen from Cos cells was associated with the nuclear matrix, a high proportion (25 to 50%) of C6 T antigen was bound to this structure. Results obtained from lytically infected monkey cells showed that early in infection, before viral replication was initiated, a higher proportion (22%) of T antigen was found associated with the nuclear matrix compared with amounts found associated with this structure later in infection (5 to 8%). These results suggest that an increased association of T antigen with this structure is not correlated with viral replication. T antigen isolated from the C6 nuclear matrix was more highly phosphorylated than was soluble C6 T antigen and was capable of binding to the host p53 protein. C6 DNA contains three mutations: two corresponding to N-terminal changes at amino acid positions 30 and 51 and a third located internally at amino acid position 153. By analysis of the subnuclear distribution of T antigen from rat cells transformed by C6 submutant T antigens, it was determined that one or both of the mutations at the NH2 terminus are responsible for the increased quantity of C6 T antigen associated with the nuclear matrix. These results suggest that neither a functional viral DNA replication origin nor the origin binding property of T antigen is required for association of this protein with the nuclear matrix.
D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000956:Antigens, Viral / Q000032:analysis; D000957:Antigens, Viral, Tumor / Q000235:genetics* / Q000302:isolation & purification; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D002472:Cell Transformation, Viral; D002522:Chlorocebus aethiops; D005455:Fluorescent Antibody Technique; D007668:Kidney; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics*; D013539:Simian virus 40 / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics* / Q000302:isolation & purification
D000952:Antigens, Polyomavirus Transforming; D000956:Antigens, Viral; D000957:Antigens, Viral, Tumor; D014764:Viral Proteins; D011494:Protein Kinases