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Bovine papilloma virus-transformed cells contain multiple E2 proteins
N L Hubbert1, J T Schiller, D R Lowy
1Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD 20892.
Summary
The bovine papilloma virus type 1 (BPV) E2 open reading frame produces multiple proteins. These include a trans-activating protein and smaller inhibitory proteins that regulate viral gene expression.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- The bovine papilloma virus type 1 (BPV) E2 open reading frame (ORF) is known to regulate viral gene expression.
- Genetic evidence suggests the E2 ORF encodes at least two distinct gene products with regulatory functions.
Purpose of the Study:
- To identify and characterize the proteins encoded by the BPV E2 ORF.
- To investigate the roles of these proteins in regulating viral transcription.
Main Methods:
- Analysis of proteins from wild-type BPV-transformed cells using SDS-PAGE.
- Pulse-chase experiments to determine protein half-lives and precursor-product relationships.
- Subcellular fractionation to localize E2 proteins within the cell.
Main Results:
- Three E2-encoded proteins with apparent molecular masses of 48, 31, and 28 kDa were identified.
- The 48-kDa protein, corresponding to the full-length product, exhibits trans-activating activity.
- The 31- and 28-kDa proteins, containing carboxyl-terminal sequences, likely function as inhibitory E2 proteins.
- All three E2 proteins were localized to the nucleus.
- The presumptive repressor (31-kDa) protein was more abundant than the trans-activator (48-kDa) in BPV-transformed cells.
Conclusions:
- The BPV E2 ORF encodes multiple proteins, including a trans-activator and potential repressors.
- These E2 proteins play a crucial role in the regulation of BPV gene expression.
- The relative abundance of these proteins may influence the rate of viral transcription.