Temperature-restricted mutants of human adenovirus type 5. In: strategy of the viral genome

Adenovirus type 12 E1B 19-kilodalton protein is not required for oncogenic transformation in rats

The adenovirus type 12 mutants in700 and pm700 carry site-specific mutations within the reading frame encoding the E1B 19-kilodalton protein (19K protein) which prevent the production of the intact 19K protein. In cultures of human A549 cells, these mutants grow just as well as the wild-type virus does, but they display a large-plaque (lp), cytocidal (cyt) phenotype. DNA in these infected cells is not degraded, but at late times in human KB cells infected by the mutants, the mutants display a DNA degradation (deg) phenotype. The transformation phenotype of these mutants is also host range. Although the mutants are defective for transformation of the 3Y1 rat cell line, they transform rat and mouse primary kidney cells in vitro at wild-type efficiency and are capable of inducing tumors in rats. These results support the view that the type 12 E1B 19K protein is not obligatory for oncogenic transformation.

Cellular transformation by adenovirus type 5 is influenced by the viral DNA polymerase

Early region 2B (E2B) of the group C adenoviruses encodes a number of proteins, including the 140-kilodalton DNA polymerase, which plays a role in the initiation of viral DNA replication. Temperature-sensitive (ts) mutants with mutations mapping to E2B are conditionally defective for both DNA replication in human cells and transformation of rat cells. Nucleotide sequence analysis shows that the E2B mutant ts36 possesses a single point mutation specific to the viral DNA polymerase; this transition of a C to a T at position 7623 changes leucine residue 249 in the polymerase to a phenylalanine. A wild-type (ts+) revertant possesses a codon specifying the original leucine at position 249. Phenotypic analysis of revertant and wild-type viruses derived by marker rescue from ts36 shows that these variants are wild type for both viral DNA replication and transformation. Thus, the single point mutation in the polymerase gene of ts36 is responsible for both defects.