The sequence-structure-function relationship of intrinsic ERα disorder.

Area of Science:

• Molecular Biology
• Biochemistry
• Cancer Research

Background:

• Oestrogen receptor alpha (ERα) is a key driver of breast cancer, often activated by phosphorylation at serine 118.
• The mechanism of this phosphorylation-induced ERα activation, enabling oestrogen-independent function, remains poorly understood.
• Understanding this mechanism is critical given ongoing clinical trials targeting this region with kinase inhibitors.

Purpose of the Study:

• To elucidate the molecular mechanism by which serine 118 phosphorylation affects the intrinsically disordered N-terminal domain of ERα.
• To investigate the structural and functional consequences of this phosphorylation event.
• To provide mechanistic insights into intrinsically disordered proteins and nuclear receptor function.

Main Methods:

• Integration of small-angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) spectroscopy.
• Functional studies, including mutational analysis (S118A mutation).
• Assays for ER transcriptional activity, target-gene expression, and cell growth.

Main Results:

• Serine 118 phosphorylation induces an unexpected expansion of the ERα disordered N-terminal domain.
• This expansion disrupts specific hydrophobic clustering between two aromatic-rich regions within the domain.
• Mutations mimicking this disruption rescue transcriptional activity, gene expression, and cell growth impaired by the S118A mutation.

Conclusions:

• ERα function is regulated by phosphorylation-induced structural changes in its disordered domain, driven by hydrophobic interactions.
• These findings challenge purely electrostatic models and offer fundamental insights into intrinsically disordered protein regulation.
• This work advances the understanding of ERα disorder, crucial for developing targeted breast cancer therapeutics.