UHRF1/UBE2L6/UBR4-mediated ubiquitination regulates EZH2 abundance and thereby melanocytic differentiation phenotypes in melanoma.
Gamze Kuser-AbaliYoufang ZhangPacman SzetoPeinan ZhaoSamar Masoumi-MoghaddamClare G FedeleIsobel LeeceCheng HuangJen G CheungMalaka AmeratungaFumihito NoguchiMiles C AndrewsNicholas C WongRalf Bernd SchittenhelmMark ShackletonPublished in: Oncogene (2023)
Cellular heterogeneity in cancer is linked to disease progression and therapy response, although mechanisms regulating distinct cellular states within tumors are not well understood. We identified melanin pigment content as a major source of cellular heterogeneity in melanoma and compared RNAseq data from high-pigmented (HPCs) and low-pigmented melanoma cells (LPCs), suggesting EZH2 as a master regulator of these states. EZH2 protein was found to be upregulated in LPCs and inversely correlated with melanin deposition in pigmented patient melanomas. Surprisingly, conventional EZH2 methyltransferase inhibitors, GSK126 and EPZ6438, had no effect on LPC survival, clonogenicity and pigmentation, despite fully inhibiting methyltransferase activity. In contrast, EZH2 silencing by siRNA or degradation by DZNep or MS1943 inhibited growth of LPCs and induced HPCs. As the proteasomal inhibitor MG132 induced EZH2 protein in HPCs, we evaluated ubiquitin pathway proteins in HPC vs LPCs. Biochemical assays and animal studies demonstrated that in LPCs, the E2-conjugating enzyme UBE2L6 depletes EZH2 protein in cooperation with UBR4, an E3 ligase, via ubiquitination at EZH2's K381 residue, and is downregulated in LPCs by UHRF1-mediated CpG methylation. Targeting UHRF1/UBE2L6/UBR4-mediated regulation of EZH2 offers potential for modulating the activity of this oncoprotein in contexts in which conventional EZH2 methyltransferase inhibitors are ineffective.
Keyphrases
- long noncoding rna
- long non coding rna
- signaling pathway
- single cell
- magnetic resonance
- dna methylation
- mass spectrometry
- high glucose
- magnetic resonance imaging
- high throughput
- stem cells
- squamous cell carcinoma
- machine learning
- ms ms
- diabetic rats
- gene expression
- endothelial cells
- cancer therapy
- wastewater treatment
- cell proliferation
- genome wide
- bone marrow
- binding protein
- basal cell carcinoma
- case report
- big data
- electronic health record
- smoking cessation
- replacement therapy