Ube2s regulates Sox2 stability and mouse ES cell maintenance

Area of Science:

• Stem cell biology
• Molecular and cell biology
• Epigenetics and gene regulation

Background:

• Sox2 is crucial for embryonic stem (ES) cell pluripotency and differentiation, with its activity being dosage-dependent.
• Transcriptional regulation of Sox2 is well-studied, but mechanisms controlling its protein degradation are largely unknown.

Purpose of the Study:

• To identify novel mechanisms regulating Sox2 protein stability.
• To elucidate the role of Sox2 degradation in maintaining ES cell identity and preventing differentiation.

Main Methods:

• Proteomic analysis to identify Sox2-interacting proteins.
• Ubiquitination assays to determine the type of ubiquitination mediated by Ube2s.
• Western blotting and immunofluorescence to assess Sox2 protein levels and localization.
• Cellular assays to evaluate ES cell self-renewal and differentiation potential.

Main Results:

• Ubiquitin-conjugating enzyme E2S (Ube2s) was identified as a novel effector for Sox2 protein degradation.
• Ube2s mediates the formation of K11-linked polyubiquitin chains at the K123 residue of Sox2.
• This ubiquitination targets Sox2 for proteasome-mediated degradation, thereby fine-tuning its protein levels.
• Ube2s activity reinforces ES cell self-renewal and pluripotency and represses Sox2-driven neural ectodermal differentiation.

Conclusions:

• Ube2s is a key regulator of Sox2 protein stability through K11-linked polyubiquitination and proteasomal degradation.
• Ube2s plays a critical role in maintaining the pluripotent state of ES cells by controlling Sox2 levels.
• Ube2s acts as a tumor suppressor by preventing Sox2-mediated differentiation into neural lineages.