Biochemical procedure for production of small deletions in simian virus 40 DNA

A simple biochemical procedure for producing small deletions (15 to 50 base pairs) at virtually any location in simian virus 40 DNA has been developed. The steps involved are: cleavage of the closed-circular DNA to produce a linear structure followed by 5'-exonuclease digestion to expose a short single-stranded segment at each 3' end of the molecule. Mutants containing deletions at the site of the cleavage are obtained by infecting permissive monkey kidney cells with the exonuclease-treated DNA in the presence or absence of a helper DNA (depending upon whether or not the site of cleavage and therefore the deletion occurred in a gene required for vegetative multiplication). In this paper viable mutants with deletions at the HpaII endonuclease cleavage site (0.735 map position) and defective trans-complementable mutants with deletions at the EcoRI endonuclease cleavage site (0/1.0 map position) were isolated.