Simian virus 40 T antigen binds to host cell chromosomes

Abstract

T ANTIGEN of simian virus 40 (SV40) is the product of the A gene of the virus¹ and has been shown to have a role in the establishment and maintenance of transformation^2–5. T antigen has also been shown to be required for the initiation of each round of viral DNA synthesis6 and for induction of host DNA synthesis^7–11. Furthermore, it has been suggested that T antigen may initiate DNA synthesis in transformed cells and thereby help maintain those cells in the transformed state^6,12–14. The SV40 genome has three preferential binding sites for T antigen, one of which is at or near the site at which viral DNA synthesis is initiated¹⁵. The binding of T antigen to eukaryote DNA is less well defined but shows a preference for double-stranded over single-stranded DNA¹⁶. Similar findings have been reported for tumour-specific transplantation antigen¹⁷. SV40 nucleohistone has also been reported to bind T antigen in amounts threefold greater than does native SV40 DNA¹⁸. To investigate the role of T antigen in the regulation of the host cell, we have asked whether host chromosomes bind detectable amounts of T antigen; and, if so, whether the binding is restricted to specific chromosomes or to specific chromosomal loci. Although earlier studies have suggested that T antigen is associated with nuclear chromatin of infected cells¹⁹, this study is the first to report the binding of SV40 T antigen to mammalian chromosomes.