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Deletion mutants of region E1a of AD12 E1 plasmids: effect on oncogenic transformation
Abstract:
Plasmids containing the E1 region of Ad12 DNA can transform certain rodent cells into oncogenic cells. To study the role of the E1a subregion in the process of oncogenic transformation, Ad12 region E1 mutants carrying deletions in the E1a region were constructed. Deletion mutants pR7 and pR8 affect only the 13 S mRNA species encoded by region E1a, whereas deletion mutants pR11 and pR15 damage both the 12 S and 13 S E1a mRNA. All four mutants have lost their capacity to transform primary cultures of baby rat kidney cells, indicating that the E1a gene product encoded by 13 S mRNA is essential for transformation. It was further found that the mutated E1a regions of both pR7 and pR11 can induce expression of region E1b, which implies that the transformation deficiency of these mutants is not due to the inability to activate E1b expression. Surprisingly, the transforming capacity of pR7 and pR11 is restored when these mutant E1 regions are covalently coupled to the SV40 "enhancer" region. Cells transformed by these hybrids plasmids, however, were not tumorigenic in nude mice.
Insights
The E1a gene product from 13S mRNA is crucial for Ad12 oncogenic transformation of rodent cells. Restoration of transforming capacity in Ad12 E1a mutants by SV40 enhancer coupling did not result in tumorigenicity.
Area of Science:
- Molecular Biology
- Oncology
- Virology
Background:
- Adenovirus type 12 (Ad12) DNA's E1 region can oncogenically transform rodent cells.
- The E1a subregion of Ad12 is implicated in this oncogenic transformation process.
Purpose of the Study:
- To investigate the specific role of the E1a subregion in Ad12-mediated oncogenic transformation.
- To determine which E1a mRNA species are essential for cell transformation.
Main Methods:
- Construction of Ad12 E1 deletion mutants (pR7, pR8, pR11, pR15) targeting the E1a region.
- Assay of transformation capacity in primary baby rat kidney cell cultures.
- Analysis of E1b expression induction by mutated E1a regions.
- Covalent coupling of mutant E1 regions to the SV40 enhancer region.
Main Results:
- All four E1a deletion mutants (pR7, pR8, pR11, pR15) lost their transforming capacity.
- The 13S mRNA-encoded E1a gene product is essential for transformation.
- Mutants pR7 and pR11 retained the ability to induce E1b expression.
- Coupling of pR7 and pR11 E1 regions to the SV40 enhancer restored transforming capacity, but resulted in non-tumorigenic cells.
Conclusions:
- The 13S mRNA species of Ad12 E1a is essential for oncogenic transformation of baby rat kidney cells.
- The E1a region's transforming function can be influenced by external elements like the SV40 enhancer, altering cellular oncogenicity.