Related Experiment Videos
Phosphorylated 350 kD protein in the nucleus as it is associated with cell transformation
Abstract:
Protein kinases are thought to play a key role in signal transduction and oncogenesis, but little is known about the intranuclear phosphorylation events associated with transformation. Here we report on cell cycle-dependent phosphorylation of cytoskeleton-associated 350 kD protein and the regular interchange in its location between the nucleus and cytoplasm of normal cells. Persistent intranuclear location of the phosphorylated 350 kD protein was also found throughout the cell cycle in transformed cells, as detected by immunoprecipitation of 32P-phosphorylated 350 kD protein from isolated nuclei and immunofluorescent staining with a monoclonal antibody that recognized phosphorylated site of 350 kD protein. A conditional transformed phenotype induced by a temperature-sensitive (ts) viral oncogene or a transforming growth factor was also associated with the intranuclear presence of the phosphorylated 350 kD protein. Thus the 350 kD protein seems to be a target molecule of protein kinases that are stimulated directly or indirectly by growth factors or by oncogene products in the nucleus, and appears to be a new transformation-related nuclear antigen.
Insights
Phosphorylation of a 350 kD protein shifts its location to the nucleus in cancer cells, indicating its role in oncogenesis. This transformation-related nuclear antigen is a potential target for cancer therapies.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Protein kinases are crucial in cell signaling and cancer development.
- Intranuclear phosphorylation events linked to cell transformation remain poorly understood.
Purpose of the Study:
- To investigate the role of intranuclear protein phosphorylation in cell transformation.
- To identify novel transformation-related nuclear antigens.
Main Methods:
- Immunoprecipitation of 32P-phosphorylated 350 kD protein from isolated nuclei.
- Immunofluorescent staining using a monoclonal antibody against the phosphorylated site.
- Analysis of protein localization in normal and transformed cells throughout the cell cycle.
Main Results:
- Identified cell cycle-dependent phosphorylation of a 350 kD cytoskeleton-associated protein.
- Observed a shift in the protein's localization from cytoplasmic/nuclear exchange in normal cells to persistent intranuclear presence in transformed cells.
- Demonstrated that temperature-sensitive viral oncogenes and transforming growth factors induce intranuclear localization of the phosphorylated 350 kD protein.
Conclusions:
- The 350 kD protein is a nuclear target of protein kinases activated by growth factors or oncogenes.
- The phosphorylated 350 kD protein represents a new transformation-related nuclear antigen.
- This finding offers insights into molecular mechanisms of oncogenesis and potential therapeutic targets.