Physiologic activation of estrogen receptor α (ERα) is mediated by estradiol (E2) binding in the ligand-binding pocket of the receptor, repositioning helix 12 (H12) to facilitate binding of coactivator proteins in the unoccupied coactivator binding groove. In breast cancer, activation of ERα is often observed through point mutations that lead to the same H12 repositioning in the absence of E2. Through expanded genetic sequencing of breast cancer patients, we identified a collection of mutations located far from H12 but nonetheless capable of promoting E2-independent transcription and breast cancer cell growth. Using machine learning and computational structure analyses, this set of mutants was inferred to act distinctly from the H12-repositioning mutants and instead was associated with conformational changes across the ERα dimer interface. Through both in vitro and in-cell assays of full-length ERα protein and isolated ligand-binding domain, we found that these mutants promoted ERα dimerization, stability, and nuclear localization. Point mutations that selectively disrupted dimerization abrogated E2-independent transcriptional activity of these dimer-promoting mutants. The results reveal a distinct mechanism for activation of ERα function through enforced receptor dimerization and suggest dimer disruption as a potential therapeutic strategy to treat ER-dependent cancers.

中文翻译：

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诱导二聚化的体细胞雌激素受体α突变促进受体活性和乳腺癌增殖

雌激素受体 α (ERα) 的生理激活是通过雌二醇 (E2) 结合在受体的配体结合口袋中介导的，重新定位螺旋 12 (H12) 以促进共激活蛋白在未占据的共激活蛋白结合槽中的结合。在乳腺癌中，ERα 的激活通常通过点突变观察到，点突变导致在 E2 缺失的情况下相同的 H12 重新定位。通过对乳腺癌患者进行扩展基因测序，我们发现了一系列远离 H12 但仍能够促进不依赖于 E2 的转录和乳腺癌细胞生长的突变。使用机器学习和计算结构分析，推断这组突变体的作用与 H12 重定位突变体不同，而是与 ERα 二聚体界面的构象变化相关。通过全长 ERα 蛋白和分离的配体结合域的体外和细胞内测定，我们发现这些突变体促进 ERα 二聚化、稳定性和核定位。选择性破坏二聚化的点突变消除了这些二聚体促进突变体的不依赖于 E2 的转录活性。结果揭示了通过强制受体二聚化激活 ERα 功能的独特机制，并表明二聚体破坏是治疗 ER 依赖性癌症的潜在治疗策略。