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Cell type dependent transformation by adenovirus 5 E1a proteins
1Institute for Molecular Virology, St. Louis University Medical Center, Missouri 63110.
Abstract:
The two major proteins of 243 amino acids (243R) and 289R encoded by the E1a region of adenovirus 5 are related, differing only by the presence of an internal conserved 46 amino acid segment in the 289R protein. We report here that these proteins have different cell transformation properties. Primary baby rat kidney (BRK) cells infected with an M-MuLV retrovirus vector that expresses the 243R protein are immortalized and the resulting foci consist predominantly of epithelial cells; a small fraction of the foci consist of fibroblast-like cells. In contrast, BRK cells infected with a retrovirus expressing the 289R protein are immortalized at a very low frequency and the foci induced consist of only fibroblast-like cells. The immortalizing properties of the 289R protein are dramatically changed by certain mutations within the unique 46 amino acid region: M-MuLV vectors with these mutations immortalize epithelial cells with high efficiency, as much as an order of magnitude higher than vectors that express the 243R protein. The enhanced immortalization property of the mutant forms of the 289R protein does not appear to be related to their transcriptional activation function. Our results suggest that the unique region of the 289R protein has the potential to inhibit immortalization of primary epithelial cells.
Insights
Adenovirus E1a proteins 243R and 289R exhibit distinct cell transformation abilities. Mutations in the 289R protein
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- Adenovirus type 5 E1a region encodes two related proteins, 243R and 289R, differing by a 46-amino acid segment.
- These proteins play critical roles in viral replication and cellular transformation.
Purpose of the Study:
- To investigate and compare the distinct cell transformation properties of adenovirus 243R and 289R proteins.
- To elucidate the role of the unique 46-amino acid region in the 289R protein's transformation activity.
Main Methods:
- Utilized Moloney murine leukemia virus (M-MuLV) retroviral vectors to express 243R and 289R proteins in primary baby rat kidney (BRK) cells.
- Assessed cell immortalization efficiency and characterized the resulting cell foci (epithelial vs. fibroblast-like).
- Introduced mutations into the unique 46-amino acid region of the 289R protein to evaluate their impact on transformation.
Main Results:
- The 243R protein efficiently immortalized BRK cells, yielding predominantly epithelial cell foci.
- The 289R protein immortalized BRK cells at a very low frequency, producing only fibroblast-like foci.
- Mutations in the 46-amino acid region of 289R significantly enhanced epithelial cell immortalization, exceeding the efficiency of 243R.
- The enhanced immortalization by mutant 289R proteins was independent of transcriptional activation function.
Conclusions:
- The unique 46-amino acid region of the 289R protein possesses inhibitory potential against primary epithelial cell immortalization.
- Differential cell transformation properties of 243R and 289R proteins are mediated by the unique 46-amino acid segment.