A small subclass of SV40 T antigen binds to the viral origin of replication

Cell. 1982 Jun;29(2):375-83. doi: 10.1016/0092-8674(82)90154-4.

Abstract

We examined the affinities of SV40 large T antigen for unique viral DNA sequences by binding SV40 Bst NI DNA fragments in extracts of infected or transformed cells, and then immunoprecipitating the T antigen-DNA complex. The G fragment, which spans the viral origin of replication (ori) was quantitatively bound to T antigen. A T-antigen-specific monoclonal antibody (McI 7), which recognized only 5%-10% of the T antigen from infected or transformed cells, immunoprecipitated the majority of the ori-binding activity. This suggests that only a minor subclass of wild-type T antigen is active in binding to the origin. C6 cells contain a replication-defective mutant T antigen that when tested in the DNA-binding immunoassay, showed no affinity for the ori fragment. McI 7 not only failed to immunoprecipitate ori binding in C6 cells, but also did not detect any labeled C6 T antigen whatever. Thus McI 7 recognizes an immunologically distinct subset of wild-type 7 antigen that comprises the origin-binding form of the viral protein, which is absent in the C6 T antigen population. McI 122, which recognizes a 53 kilodalton host protein that complexes with T antigen, immunoprecipitated ori-binding activity from extracts of infected or transformed cells, but not from C6 cells. Thus wild-type T antigen can bind ori sequences even when complexed to the host protein. These data suggest that T antigen consists of different subpopulations with different functions.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / immunology
  • Antigens, Viral / immunology
  • Antigens, Viral / physiology*
  • Antigens, Viral, Tumor
  • Base Sequence
  • Carrier Proteins
  • Cell Transformation, Viral
  • Cells, Cultured
  • DNA, Viral / physiology*
  • DNA-Binding Proteins
  • Simian virus 40 / immunology*
  • Simian virus 40 / physiology
  • Viral Proteins / physiology
  • Virus Replication

Substances

  • Antibodies, Monoclonal
  • Antigens, Viral
  • Antigens, Viral, Tumor
  • Carrier Proteins
  • DNA, Viral
  • DNA-Binding Proteins
  • Viral Proteins