21:T429,Regulation of RNA substrate selectivity of m⁶A demethylase ALKBH5 remains elusive. Here, we identify RNA-binding motif protein 33 (RBM33) as a previously unrecognized m⁶A-binding protein that plays a critical role in ALKBH5-mediated mRNA m⁶A demethylation of a subset of mRNA transcripts by forming a complex with ALKBH5. RBM33 recruits ALKBH5 to its m⁶A-marked substrate and activates ALKBH5 demethylase activity through the removal of its SUMOylation. We further demonstrate that RBM33 is critical for the tumorigenesis of head-neck squamous cell carcinoma (HNSCC). RBM33 promotes autophagy by recruiting ALKBH5 to demethylate and stabilize DDIT4 mRNA, which is responsible for the oncogenic function of RBM33 in HNSCC cells. Altogether, our study uncovers the mechanism of selectively demethylate m⁶A methylation of a subset of transcripts during tumorigenesis that may explain demethylation selectivity in other cellular processes, and we showed its importance in the maintenance of tumorigenesis of HNSCC.22:T443,Oligomerization of DNMT3B, a mammalian de novo DNA methyltransferase, critically regulates its chromatin targeting and DNA methylation activities. However, how the N-terminal PWWP and ADD domains interplay with the C-terminal methyltransferase (MTase) domain in regulating the dynamic assembly of DNMT3B remains unclear. Here, we report the cryo-EM structure of DNMT3B under various oligomerization states. The ADD domain of DNMT3B interacts with the MTase domain to form an autoinhibitory conformation, resembling the previously observed DNMT3A autoinhibition. Our combined structural and biochemical study further identifies a role for the PWWP domain and its associated ICF mutation in the allosteric regulation of DNMT3B tetramer, and a differential functional impact on DNMT3B by potential ADD-H3K4me0 and PWWP-H3K36me3 bindings. In addition, our comparative structural analysis reveals a coupling between DNMT3B oligomerization and folding of its substrate-binding sites. Together, this study provides mechanistic insights into the allosteric regulation and dynamic assembly of DNMT3B.

	Year	Citations

About