Recombination in SV40-infected cells: Viral DNA sequences at sites of circularization of transfecting linear DNA

Abstract

When permissive monkey kidney cells are infected with linear SV40 DNA molecules, deletion mutants are generated when the termini of the linear viral DNA molecule join ( C. J. Lai and D. Nathans, 1974, J. Mol. Biol., 89, 179–193). Analysis of the joints in several of these deletion mutants indicates that joining occurs in the presence of little or no homology. In two mutants the joint is formed at a trinucleotide (in dl 1073) or tetranucleotide (in dl 1076) common to the junction of the joining sequences. In two other mutants extraneous bases have been inserted at the joint. Given the same infecting linear DNAs ( HpaII generated), for which there is no constraint on the selection of deletion mutants, the cell joins the ends of these molecules in different ways suggesting that more than one mechanism is involved in the cell-mediated cyclization of linear DNA.