Summary auto-generated
This study identifies the adenovirus type 5 (Ad5) viral functions responsible for inducing chromosomal aberrations in human embryonic kidney cells. Researchers infected cells with wild-type and mutant Ad5 viruses and analyzed chromosomal damage using cytogenetic methods. The results demonstrate that expression of the early region 1A (E1A) gene products is necessary for inducing chromosomal gaps and breaks, while other early viral genes and viral DNA replication are not required. Both major E1A proteins (243 and 289 amino acids) contribute to the effect, with the 289 amino acid protein retaining some activity alone. Specific regions are critical: deletions in the amino-terminal region of E1A proteins and throughout the transactivating domain of the 289 amino acid protein prevent damage induction. The damage primarily manifests as chromatid aberrations occurring during the G2 phase of the cell cycle, though infection must occur in G1/S phase. The study maps E1A functions important for chromosomal damage to specific domains and shows these functions are distinct from other known E1A activities like trans-activation.
Key findings
- E1A gene expression is both necessary and sufficient for Ad5-induced chromosomal aberrations in human cells, while E1B, E2, and viral DNA replication are not required
- Both the 243 and 289 amino acid E1A protein isoforms contribute to chromosomal damage at wild-type levels, though the 289 amino acid protein retains detectable activity alone
- Critical regions for damage induction include the amino-terminal region and the transactivating domain of the 289 amino acid E1A protein; specific deletions in these regions abolish the cytogenetic effect
- The ability to induce chromosomal damage correlates strongly with E1A trans-activation function but involves additional E1A properties, as evidenced by trans-activation-positive mutants that remain defective for damage
- Chromosomal damage occurs primarily as chromatid aberrations in G2 phase cells, requiring infection during G1/S phase and approximately 15 hours for accumulation of necessary viral and cellular products
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Abstract
Infection of human embryonic kidney cells with adenovirus type 5 (Ad5) induces aberrations (gaps and breaks) in the cell chromosomes. We have conducted a study utilizing a large number of Ad5 mutants to identify the viral functions that are responsible for the occurrence of cytogenetic damage. The results of our investigation have indicated that expression of the gene products of the Ad5 early region 1A (E1A) is necessary for the induction of chromosomal aberrations and that other early viral gene products do not appear to contribute to this phenotype. We have also shown that expression of both the major E1A gene products, the 243 amino acid and the 289 amino acid proteins, is required for induction of damage at wild-type levels, although the 289 amino acid protein appears to retain detectable activity on its own. Lastly, we have observed that deletions in the amino-terminal region of the E1A proteins and in the transactivating domain of the 289 amino acid protein prevent the occurrence of cytogenetic damage, whereas mutations elsewhere in the proteins do not affect this process.