Molecular cloning and comparative analyses of the genomes of simian sarcoma virus and its associated helper virus.

Abstract

Closed circular viral DNA of simian sarcoma virus (SSV) and simian sarcoma-associated virus (SSAV) obtained from acutely infected dog cells was purified on preparative agarose gels, cleaved with EcoRI, and cloned in the phage .lambda. vector Charon 21A. The cloned 9-kilobase SSAV genome (B11) has the same restriction map as the bulk of the unintegrated linear SSAV DNA intermediate. Heteroduplex analysis between an SSV clone (.lambda.-C60) and an SSAV clone (.lambda.-B11) showed 2 substitution loops and 1 deletion loop. Detailed restriction enzyme mapping and EM analysis was used to show that one of the substitution loops corresponds to an inversion of 1 of the 2 long terminal repeat units and adjacent cellular sequences in C60. The other substitution loop mapped close to the 3'' long terminal repeat. At least part of this region contained SSV-specific sequences not shared by SSAV. The 1.9-kilobase deletion mapped at 3.5-5.5 kilobases of the linear SSAV genome, corresponding to most, if not all, of the pol gene.