BIOCHEMICAL STUDIES ON ADENOVIRUS MULTIPLICATION, VI. PROPERTIES OF HIGHLY PURIFIED TUMORIGENIC HUMAN ADENOVIRUSES AND THEIR DNA's

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Abstract
Tumorigenic human adenovirus types 12 (four strains) and 18 have been purified and studied. Adenovirus types 12 and 18 contain less DNA (11-12% DNA) than do nontumorigenic adenovirus types 2 and 4 (13-14% DNA). The difference in DNA content was further shown by the physical separation of the tumorigenic from the nontumorigenic adenoviruses by analytical density-gradient equilibrium centrifuga-tion in cesium chloride; as predicted from a lower DNA content, tumorigenic adenovirus types 12 and 18 have lower buoyant densities than nontumorigenic adenovirus types 2 and 4. Purified adenovirus type 12 (prototype strain) induced tumors within three weeks after inoculation of newborn hamsters. Tumors were induced with 0.2 [mu]g of virus. The induction of tumors with three other strains of adenovirus type 12 and adenovirus type 18 required larger amounts of virus and longer time periods. Analytical centrifugation and zone centrifugation measurements on the DNA''s from adenovirus types 2 and 12 provided evidence for a high degree of homogeneity. DNA from adenovirus type 12 sedimented at a 2-3 per cent lower rate than the DNA of adenovirus type 2. These data are consistent with the results of chemical analyses and indicate that the molecular weights of the DNA''s of the tumorigenic adenoviruses are about 6-12 per cent lower than those of the nontumorigenic adenoviruses. Thermal denaturation and buoyant density measurements on the viral DNA''s showed that the DNA''s of tumorigenic adenovirus types 12 and 18 possess markedly lower denaturation temperatures and buoyant densities than the DNA''s of nontumorigenic adenovirus types 2 and 4. From these data, it is calculated that the DNA''s of adenovirus types 12 and 18 contain 48-49 per cent guanine plus cytosine, while those of adenovirus types 2 and 4 contain 56-57 per cent guanine plus cytosine. This remarkably different base composition for genetically related viruses is unexpected, and its significance remains to be established.

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