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A novel 39-kilodalton membrane protein binds GTP in polyomavirus-transformed cells
1Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Abstract:
To investigate the possible involvement of GTP-binding proteins in transformation by the DNA tumor virus polyomavirus, the GTP-binding activities of Ras-like proteins and G protein alpha subunit proteins were examined in polyomavirus-transformed cells. No differences in the degrees or patterns of expression of Ras-like proteins were observed. However, a 39-kDa protein specifically bound GTP in membranes from polyomavirus-transformed cells. This protein was not seen in nontransformed or lytically infected cells or in phenotypically normal revertants of polyomavirus-transformed cells. It reappeared, however, in spontaneous retransformants derived from the revertants. The 39-kDa protein was not found stably associated with polyomavirus T antigens, nor was it phosphorylated on tyrosine. The 39-kDa protein was not recognized by an antiserum specific for members of the Gi alpha subfamily of G proteins or by antisera against all other known GTP-binding proteins of similar molecular mass. These results suggest that this novel 39-kDa GTP-binding membrane protein is observed as part of a long-term response that accompanies stable transformation by the virus.
Insights
Researchers identified a novel 39-kDa GTP-binding membrane protein in polyomavirus-transformed cells. This protein
Area of Science:
- Virology
- Molecular Biology
- Cellular Biology
Background:
- Polyomavirus is a DNA tumor virus known to cause cell transformation.
- GTP-binding proteins play crucial roles in cellular signaling and transformation processes.
- Previous studies have not fully elucidated the role of specific GTP-binding proteins in polyomavirus-induced transformation.
Purpose of the Study:
- To investigate the involvement of GTP-binding proteins in polyomavirus-mediated cell transformation.
- To identify novel GTP-binding proteins associated with stable transformation by polyomavirus.
Main Methods:
- Examined GTP-binding activities of Ras-like proteins and G protein alpha subunits in polyomavirus-transformed cells.
- Utilized cell membrane preparations for GTP-binding assays.
- Employed Western blot analysis with specific antisera to identify the 39-kDa protein.
Main Results:
- No significant changes were observed in Ras-like protein expression.
- A novel 39-kDa GTP-binding membrane protein was specifically detected in polyomavirus-transformed cells.
- This 39-kDa protein was absent in non-transformed cells, lytically infected cells, and revertants, but reappeared in retransformants.
Conclusions:
- The novel 39-kDa GTP-binding membrane protein is a potential marker for stable polyomavirus-induced cell transformation.
- This protein is not a known Ras-like protein or a member of the Gi alpha subfamily of G proteins.
- Its presence suggests a long-term cellular response associated with viral transformation.