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The putative tumor suppressor BIN1 is a short-lived nuclear phosphoprotein, the localization of which is altered in
R Wechsler-Reya1, K Elliott, M Herlyn
1The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
Abstract:
BIN1 is a putative tumor suppressor that was identified in a genetic screen for polypeptides that interact with the MYC oncoprotein. Using a set of six monoclonal antibodies, we identified and examined biochemical features and localization of cellular BIN1. Epitope mapping indicated that a putative nuclear localization motif and the MYC-binding domain were among the regions recognized by five antibodies. In immunoprecipitation and Western analyses, cellular BIN1 was identified in human and rodent cells as a monomeric phosphoprotein of M(r) approximately 70,000. Pulse-chase experiments showed that BIN1 was short-lived, with a half-life of approximately 2 h. Cell immunofluorescence experiments revealed overlapping but unique nuclear localization patterns distinguished by two different antibodies. In normal cells, BIN1 was predominantly nucleoplasmic but was also present in a subnuclear compartment. Conversely, in a panel of tumor cells that expressed BIN1, the predominant localization was the subnuclear compartment. Taken together, the results suggested that the antibodies recognized different isoforms or conformations of BIN1, the localization of which varied between normal and tumor cells. This study will facilitate further analysis of the structure and regulation of BIN1 in normal and malignant cells.
Insights
The BIN1 protein, a potential tumor suppressor interacting with MYC, shows distinct cellular localization in normal versus tumor cells. Its varied nuclear and subnuclear patterns suggest different isoforms or conformations, impacting cancer cell regulation.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- BIN1 (Bridging Integrator 1) is identified as a potential tumor suppressor through its interaction with the MYC oncoprotein.
- Understanding BIN1's biochemical properties and cellular localization is crucial for elucidating its role in normal and malignant cells.
Purpose of the Study:
- To characterize the biochemical features and subcellular localization of cellular BIN1 using a panel of monoclonal antibodies.
- To investigate potential differences in BIN1 localization between normal and tumor cells.
Main Methods:
- Utilized six monoclonal antibodies for epitope mapping, immunoprecipitation, Western blotting, pulse-chase experiments, and immunofluorescence.
- Analyzed BIN1's molecular weight, phosphorylation status, half-life, and subcellular distribution in human and rodent cell lines.
Main Results:
- Identified BIN1 as a monomeric phosphoprotein (~70 kDa) with a short half-life (approx. 2 hours).
- Observed distinct nuclear and subnuclear localization patterns for BIN1, varying between normal and tumor cells.
- Antibody-dependent epitope mapping suggested recognition of different BIN1 isoforms or conformations.
Conclusions:
- BIN1 exhibits differential subcellular localization in normal versus tumor cells, indicating potential isoform or conformational variations.
- These findings provide a foundation for further research into BIN1's structure, regulation, and function in cancer.