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Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay
09:07

Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay

Published on: December 19, 2018

V-erba homodimers mediate the potent dominant negative activity of v-erba on everted repeats

Inna Zubkova1, Jose S Subauste

  • 1G. V Montgomery Veterans Administration Medical Center and Division of Endocrinology and Metabolism, University of Mississippi, Jackson, MS 39216, USA.

Molecular Biology Reports
|August 6, 2004
PubMed

Insights

The oncoprotein v-erbA, a mutated thyroid hormone receptor, primarily uses homodimers, not heterodimers with RXR, to exert its dominant-negative effects on Estrogen Response elements (ERs). This clarifies v-erbA

Area of Science:

  • Molecular Endocrinology
  • Oncogenesis
  • Nuclear Receptor Signaling

Background:

  • The oncoprotein v-erbA is a mutated form of thyroid hormone receptor alpha 1 (TRalpha1) that lacks thyroid hormone (T3) binding capacity.
  • v-erbA can form homodimers or heterodimers with retinoid X receptor (RXR) on specific DNA motifs like direct, everted, or inverted repeats (DRs, ERs, IRs).

Purpose of the Study:

  • To elucidate the distinct roles of v-erbA homodimers versus v-erbA-RXR heterodimers in mediating the dominant-negative activity of v-erbA.
  • To investigate the differential interactions of v-erbA homodimers and heterodimers with corepressors.

Main Methods:

  • Generation and functional characterization of v-erbA mutants, including v-erbA mutant E325A, which selectively impairs heterodimerization with RXR.
  • Analysis of v-erbA homodimerization and heterodimerization capabilities on ERs.
  • Assessment of corepressor (NCoR, SMRT) interaction preferences.

Main Results:

  • v-erbA mutant E325A demonstrates intact homodimerization but abolished heterodimerization with RXR on ERs.
  • v-erbA homodimers exhibit a preference for NCoR over SMRT, and stronger corepressor interaction compared to v-erbA-RXR heterodimers.
  • Functional studies confirm that v-erbA homodimers, not heterodimers, are responsible for the dominant-negative effects on ERs.

Conclusions:

  • v-erbA exerts its dominant-negative function primarily through homodimers, not v-erbA-RXR heterodimers.
  • Homodimerization of v-erbA is crucial for its potent inhibitory activity on Estrogen Response elements.
  • Understanding these distinct dimerization and corepressor interactions provides insight into v-erbA's oncogenic mechanism.

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