Physical organization of subgroup B human adenovirus genomes

Cleavage sites of nine bacterial restriction endonucleases were mapped in the DNA of adenovirus type 3 (Ad3) and Ad7, representative serotypes of the "weakly oncogenic" subgroup B human adenoviruses. Of 94 sites mapped, 82 were common to both serotypes, in accord with the high overall sequence homology of DNA among members of the same subgroups. Of the sites in Ad3 and Ad7 DNA, fewer than 20% corresponded to mapped restriction sites in the DNA of Ad2 or Ad5. The latter serotypes represent the "nononcogenic" subgroup C, having only 10 to 20% overall sequence homology with the DNA of subgroup B adenoviruses. Hybridization mapping of viral mRNA from Ad7-infected cells resulted in a complex physical map that was nearly identical to the map of early and late gene clusters in Ad2 DNA. Thus the DNA sequences of human adenoviruses of subgroups B and C have significantly diverged in the course of viral evolution, but the complex organization of the adenovirus genome has been rigidly conserved.