RBM33 is a unique m⁶A RNA-binding protein that regulates ALKBH5 demethylase activity and substrate selectivity

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• The regulation of m⁶A demethylase ALKBH5 substrate selectivity is not well understood.
• N⁶-methyladenosine (m⁶A) is a crucial RNA modification involved in various cellular processes.

Purpose of the Study:

• To identify novel regulators of ALKBH5 activity and elucidate their role in cancer.
• To investigate the function of RBM33 in mRNA m⁶A demethylation and head and neck squamous cell carcinoma (HNSCC) tumorigenesis.

Main Methods:

• Co-immunoprecipitation to identify protein complexes.
• RNA-binding assays to confirm m⁶A interaction.
• Western blotting to assess protein modification (SUMOylation).
• Cellular assays to evaluate autophagy and tumorigenesis.
• Analysis of DDIT4 mRNA stability and expression.

Main Results:

• RNA-binding motif protein 33 (RBM33) was identified as an m⁶A-binding protein that forms a complex with ALKBH5.
• RBM33 recruits ALKBH5 to m⁶A-modified substrates and enhances its demethylase activity by reducing ALKBH5 SUMOylation.
• RBM33 promotes HNSCC tumorigenesis by stabilizing DDIT4 mRNA through ALKBH5-mediated demethylation, thereby promoting autophagy.

Conclusions:

• RBM33 is a key regulator of ALKBH5-mediated selective mRNA demethylation.
• The RBM33-ALKBH5 complex plays a critical role in HNSCC development by modulating autophagy via DDIT4 mRNA.
• This study reveals a novel mechanism for m⁶A demethylation selectivity with implications for cancer therapy.