ERα phosphorylation at Y537 by Src triggers E6-AP-ERα binding, ERα ubiquitylation, promoter occupancy, and target...

Area of Science:

• Molecular Biology
• Cell Biology
• Endocrinology

Background:

• Transcription factors often undergo transcription-coupled proteolysis.
• Mechanisms linking estrogen receptor alpha (ERα) ubiquitylation, transcriptional activation, and proteolysis remain unclear.

Purpose of the Study:

• To elucidate the mechanisms governing ERα ubiquitylation and proteolysis upon ligand binding.
• To investigate the relationship between ERα transcriptional activation and its degradation pathway.

Main Methods:

• Investigated the cross talk between Src kinase and liganded ERα.
• Utilized in vitro assays to assess ERα phosphorylation, ubiquitylation, and degradation.
• Examined the impact of Src inhibition and ERα Y537F mutation on ERα activity and degradation.
• Assessed ERα and E6-AP binding and promoter occupancy.

Main Results:

• Liganded ERα activates and recruits Src kinase, which phosphorylates ERα at tyrosine 537 (Y537).
• ERα Y537 phosphorylation enhances binding to E6-AP, stimulating ERα ubiquitylation, target gene activation, and degradation.
• Src inhibition reduces ERα:E6-AP binding and ERα degradation.
• ERα Y537F mutation impairs estrogen-stimulated degradation and target gene activation.
• Src activation enhances ERα:E6-AP binding and promoter occupancy, boosting transcription.

Conclusions:

• ERα Y537 phosphorylation by Src is a key event linking transcriptional activation to E6-AP-mediated ubiquitylation and proteasomal degradation.
• This pathway provides a novel mechanism for fine-tuning ERα action.
• Hormonally sensitive tissues may exhibit reduced ERα protein levels despite maintained transcriptional activity.