An SV40 mutant T antigen does not bind the SV40 viral origin.

F8dl is an SV40 deletion mutant that lacks over 60% of the coding sequences for large T antigen and yet is able to immortalize early passage rat cells, to transform established cell lines, and to cause tumors in animals. We report here on the further characterization of this mutant and show that (a) transformation by F8dl is protein mediated but does not require the action of the SV40 small t antigen; (b) the F8dl T antigens have, or are associated with, an ATPase activity; (c) the 34-kDa mutant T antigen of F8dl is localized in nuclei and cell membranes of F8dl transformants and binds to double-stranded DNA; (d) the 20-25 kDa forms of the mutant T antigen are cytoplasmic; and (e) the F8dl T antigens do not bind with high affinity to the SV40 origin of viral DNA replication.