Cleavage of Simian virus 40 DNA at a unique site by a bacterial restriction enzyme

The R(1) restriction endonuclease of Escherichia coli converts covalently-closed circular Simian Virus 40 (SV40) DNA to unit-length linear duplex molecules. Cleavage occurs at a unique site, since denaturation and renaturation of these linear molecules yield linear but no circular molecules. The distance from the cleavage site to the SV40 DNA sequence contained in the adenovirus-SV40 hybrid, Ad2(+)ND(1), is 0.11 of the length of SV40 DNA. T4 gene 32 protein binds to SV40 DNA in a region 0.45 of the length of SV40 DNA from the R(1) cleavage site. E. coli B restriction endonuclease can cleave SV40 DNA at several sites.