Studies on a defective variant of simian virus 40 that is substituted with DNA sequences derived from monkey. II. Structure of DNA.

The structure of a substituted, reiterated defective variant of the simian virus 40 genome has been analyzed. The DNA of the defective variant is a closed circular duplex resistant to restriction endonuclease R-EcoRI and slightly shorter than the genome of wild type simian virus 40. Analysis of the double-stranded DNA segments produced by the action of a variety of restriction endonucleases on the defective genome allow description of the molecule as follows. (a) The full DNA molecule contains four tandem repeats of a DNA segment containing both SV40 and monkey DNA sequences. (b) Three out of the four segments are identical and are about 23% of the wild type genome in length: one segment of the four is larger and contains an additional peice of DNA about 4.3% of a wild type genome in length, but is otherwise identical with the other three segments. (c) Portions of the defective variant that contain monkey DNA can be isolated as discrete segments by restriction endonuclease digestion. (d) Some of the sequences originating from monkey DNA are derived from the highly reiterated class of monkey DNA sequences; others may represent sequences derived from infrequently reiterated or single copy monkey sequences.