UBE3A-mediated mH2A1 Ubiquitination activates TERT transcription to promote senescence resistance in pancreatic cancer.

UBE3A was significantly upregulated in pancreatic cancer tissues and correlated with poor patient outcomes.

• UBE3A expression was evaluated in pancreatic cancer tissues compared to normal tissues.
• Elevated UBE3A levels correlated with poor prognosis in pancreatic cancer patients.
• These findings were established through analysis of patient tissue samples.

UBE3A inhibits cellular senescence in pancreatic cancer cells, thereby promoting tumor proliferation and metastasis.

• Functional studies were performed using in vitro and in vivo experiments.
• Senescence was evaluated through SA-β-gal staining, EdU assays, and detection of senescence-associated markers.
• In vivo experiments included subcutaneous xenograft and liver metastasis models.
• Loss and gain of UBE3A function altered senescence phenotypes and tumor growth behavior.

Histone variant macroH2A1 (mH2A1) recruits EZH2 to mediate H3K27me3 modification, repressing TERT transcription.

• Mechanistic studies utilized ChIP-seq and RNA-seq to explore downstream pathways.
• mH2A1 was identified as a regulator of TERT transcription through epigenetic silencing.
• EZH2 recruitment by mH2A1 led to H3K27me3 modification at the TERT locus.
• Findings were validated through ChIP-qPCR and dual-luciferase reporter assays.

UBE3A interacts with mH2A1 through its N-terminal domain and induces K48-linked polyubiquitination at the K167 residue, accelerating mH2A1 degradation.

• The interaction between UBE3A and mH2A1 was identified using Ub-MS and IP-MS approaches.
• UBE3A specifically interacts with mH2A1 via its N-terminal domain.
• K48-linked polyubiquitination occurred at the K167 residue of mH2A1.
• K48-linked polyubiquitination is associated with proteasomal degradation, consistent with the ubiquitin-proteasome system.
• mH2A1 degradation was validated through ubiquitination assays.

UBE3A-mediated mH2A1 degradation upregulates TERT expression, enhancing the anti-senescence capacity of pancreatic cancer cells.

• Loss of mH2A1 via UBE3A-driven ubiquitination relieved epigenetic repression of TERT.
• Upregulated TERT enhanced resistance to cellular senescence in pancreatic cancer cells.
• This axis was confirmed to promote malignant progression downstream of UBE3A activity.

Inhibition of UBE3A combined with the senolytic agent ABT-263 induced apoptosis and inhibited tumor growth.

• ABT-263 is a senolytic agent used in combination with UBE3A inhibition.
• The combination approach induced apoptosis in pancreatic cancer cells.
• Tumor growth inhibition was demonstrated, supporting a therapeutic rationale for this combination.
• These experiments were conducted in the context of in vitro and/or in vivo tumor models.