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Specific association of estrogen receptor beta with the cell cycle spindle assembly checkpoint protein, MAD2
G Poelzl1, Y Kasai, N Mochizuki
1Molecular Cardiology Research Institute, Cardiology Division, Department of Medicine, Tufts University School of Medicine and New England Medical Center, Boston, MA 02111, USA.
Abstract:
Estrogen receptors (ERs) are ligand-activated transcription factors that regulate gene expression and cell growth. Two ERs now have been identified: ERalpha and the more recently discovered ERbeta. The physiological function of ERbeta remains unclear, but evidence from vascular injury studies and from ERbeta knockout mice suggests that ERbeta may be involved in the regulation of cellular proliferation. Here we show a direct and specific interaction between ERbeta and the cell cycle mitotic spindle assembly checkpoint protein, MAD2 (mitosis arrest-deficient 2). The ERbeta-MAD2 interaction was identified by screening of a yeast two-hybrid system vascular endothelial cell library with ERbeta and confirmed with glutathione S-transferase-fusion protein interaction studies. In contrast, ERalpha did not interact with MAD2 in either the two-hybrid system or in the protein-protein interaction experiments. Amino acids 173-208 in the hinge region of ERbeta were sufficient to mediate the interaction with MAD2 in the two-hybrid system and in glutathione S-transferase-fusion protein studies. These data identify a link between ERbeta and MAD2 of potential importance to regulation of the cell cycle and support a function of ERbeta distinct from the established role of ERs as transcription factors.
Insights
Estrogen receptor beta (ERbeta) directly interacts with the cell cycle protein MAD2. This finding suggests a novel role for ERbeta in regulating cell proliferation, distinct from its known transcription factor functions.
Area of Science:
- Molecular Biology
- Cell Biology
- Endocrinology
Background:
- Estrogen receptors (ERs) are crucial for gene expression and cell growth.
- Two ERs, ERalpha and ERbeta, are known, but ERbeta's function is less understood.
- ERbeta's potential role in cellular proliferation is suggested by vascular injury and knockout studies.
Purpose of the Study:
- To investigate the interaction between ERbeta and cell cycle proteins.
- To determine if ERbeta interacts with MAD2, a key component of the spindle assembly checkpoint.
- To elucidate ERbeta's function beyond its role as a transcription factor.
Main Methods:
- Yeast two-hybrid system screening using a vascular endothelial cell library and ERbeta.
- Glutathione S-transferase (GST)-fusion protein interaction studies to confirm findings.
- Identification of the specific ERbeta region responsible for MAD2 interaction.
Main Results:
- A direct and specific interaction was found between ERbeta and MAD2.
- ERalpha did not interact with MAD2 in the same experimental systems.
- Amino acids 173-208 in ERbeta's hinge region were sufficient for MAD2 binding.
Conclusions:
- Estrogen receptor beta directly binds to the cell cycle protein MAD2.
- This interaction highlights a novel role for ERbeta in cell cycle regulation.
- ERbeta's function extends beyond transcriptional regulation, involving direct protein-protein interactions with cell cycle machinery.