Phosphorylation of Activation Function-1 Regulates Proteasome-Dependent Nuclear Mobility and E6-Associated Protein Ubiquitin Ligase Recruitment to the Estrogen Receptor β

作者：Nathalie Picard, Catherine Charbonneau, Mélanie Sanchez, Anne Licznar, Muriel Busson, Gwendal Lazennec, André Tremblay · 发表于：Molecular Endocrinology · 年份：2007 · DOI：10.1210/me.2007-0281 · 被引用次数：66 · 研究领域：Ubiquitin and proteasome pathways、Retinoids in leukemia and cellular processes、Estrogen and related hormone effects

The ubiquitin-proteasome pathway has been recognized as an important regulator in the hormonal response by estrogen receptor (ER) alpha, but its impact on ERbeta function is poorly characterized. In the current study, we investigated the role of the ubiquitin-proteasome pathway in regulating ERbeta activity and identified regulatory sites within the activation function (AF)-1 domain that modulate ERbeta ubiquitination and nuclear dynamics in a hormone-independent manner. Although both ERalpha and ERbeta were dependent on proteasome function for their maximal response to estrogen, they were regulated differently by proteasome inhibition in the absence of hormone, an effect shown to be dependent on their respective AF-1 domain. Given the role of AF-1 phosphorylation to regulate ER activity, we found that sequential substitutions of specific serine residues contained in MAPK consensus sites conferred transcriptional activation of ERbeta in a proteasome-dependent manner through reduced ubiquitination and enhanced accumulation of mutant receptors. Specifically, serines 94 and 106 within ERbeta AF-1 domain were found to modulate subnuclear mobility of the receptor to transit between inactive clusters and a more mobile state in a proteasome-dependent manner. In addition, cellular levels of ERbeta were regulated through these sites by facilitating the recruitment of the ubiquitin ligase E6-associated protein in a phosphorylation-dependent manner. These findings suggest a role for ERb...