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Cytoplasmic p53 polypeptide is associated with ribosomes
B M Fontoura1, C A Atienza, E A Sorokina
1Department of Pathology, New York University School of Medicine, New York 10016, USA.
Molecular and Cellular Biology
|June 1, 1997
Summary
The tumor suppressor p53 protein associates with ribosomes, specifically those containing covalently modified 5.8S ribosomal RNA (rRNA). This finding reveals a novel functional link between p53 and the translation machinery.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The tumor suppressor p53 protein is known to be covalently linked to 5.8S ribosomal RNA (rRNA).
- p53 polypeptide is typically found at low basal levels in the cytoplasm during the G1 phase of the cell cycle.
Purpose of the Study:
- To investigate the association of cytoplasmic p53 polypeptide with ribosomes.
- To characterize the nature of the ribosomal association of p53, including the role of 5.8S rRNA.
Main Methods:
- Cytoplasmic extracts from rat embryo fibroblasts and MCF7 cells were treated with RNase or puromycin to assess p53-ribosome dissociation.
- Immunoprecipitation was used to isolate p53-associated ribosomes and detect 5.8S rRNA and p53 mRNA.
- Sodium dodecyl sulfate (SDS) treatment was employed to analyze 5.8S rRNA in bulk ribosomes.
Main Results:
- Both wild-type and mutant p53 polypeptides were found associated with ribosomes to varying degrees.
- RNase or puromycin treatment dissociated p53 from ribosomes, indicating a functional association.
- 5.8S rRNA in p53-associated ribosomes was covalently linked to protein, unlike in bulk ribosomes.
- p53 mRNA, but not GAPDH mRNA, was co-immunoprecipitated with cytoplasmic p53 polypeptide.
Conclusions:
- Cytoplasmic p53 polypeptide associates with a specific subset of ribosomes.
- This subset of ribosomes is characterized by the presence of covalently modified 5.8S rRNA.
- The findings suggest a novel functional role for p53 within the ribosome-associated translation machinery.