TERT Promoter Methylation Is Oxygen-Sensitive and Regulates Telomerase Activity

Area of Science:

• Epigenetics
• Stem Cell Biology
• Molecular Biology

Background:

• Telomere maintenance by telomerase is crucial for cell proliferation and differentiation.
• Telomerase reverse transcriptase (TERT) is the catalytic subunit of telomerase, and its regulation is linked to stemness and tumorigenesis.
• Oxygen levels influence cellular behaviors, but their role in TERT epigenetic regulation in embryonic stem cells (ESCs) is unclear.

Purpose of the Study:

• To investigate the role of physiological oxygen (physoxia) in the epigenetic regulation of telomerase and TERT during ESC differentiation.
• To explore the involvement of DNA methyltransferases (DNMTs) in physoxia-driven epigenetic modifications of TERT.

Main Methods:

• ESC differentiation model under ambient air versus physiological oxygen (2% O2).
• Analysis of TERT expression, telomerase activity, and TERT promoter methylation.
• Chemical inhibition of DNMT3B and Chromatin Immunoprecipitation (ChIP) for DNMT3B.

Main Results:

• Physoxia culture enhanced ESC proliferation and stemness, delaying differentiation onset compared to ambient air.
• TERT expression and telomerase activity remained elevated during differentiation under physoxia.
• TERT promoter methylation increased with differentiation in ambient air more than in physoxia.
• DNMT3B inhibition reduced TERT promoter methylation, increasing TERT gene and telomerase activity.
• DNMT3B binding to the TERT promoter correlated with TERT downregulation and increased methylation.

Conclusions:

• DNMT3B directly binds to the TERT promoter, mediating differentiation-linked TERT downregulation.
• DNMT3B's association with the TERT promoter is sensitive to oxygen levels.
• These findings reveal novel aspects of oxygen-sensitive telomerase regulation during development.