Abstract
The simian virus 40 (SV40) mutant dl1055 carries a 55 base pair deletion in the viral early region coding sequences that causes premature termination of large tumour (T) antigen translation resulting in a protein fragment consisting of the amino-terminal 399 residues. The mutation renders the virus defective. We report the characterization of hyb4001, which was isolated as a single plaque following cotransfection of permissive cells with dl1055 DNA and the DNA of a related papovavirus, simian agent 12 (SA12). Hyb4001 arose by two homologous recombination events involving crossovers in regions of 7 and 12 base pairs of perfect homology between the two viruses. Hyb4001 synthesizes a hybrid T antigen with the amino-terminal 382 residues encoded by SV40, residues 383 to 449 encoded by SA12, and the carboxy-terminal 259 residues encoded by SV40.