DNMT3B Controls Enhancer-Linked Chromatin and Cell Cycle Networks in Acute Myeloid Leukemia

<b>Background</b>: DNMT3B is frequently overexpressed in molecular subsets of acute myeloid leukemia (AML) and is associated with poor prognosis. Unlike DNMT3A, DNMT3B is rarely mutated, suggesting dysregulation through epigenetic mechanisms. The regulatory basis and downstream consequences of DNMT3B overexpression in AML remain incompletely defined. <b>Methods</b>: We integrated analyses of BeatAML, TCGA, and BLUEPRINT cohorts with multi-omic profiling (RNA-seq, DNA methylation, ATAC-seq, and proteomics) in DNMT3B-high AML models. Nanaomycin A (NanA) was used as a DNMT3B-directed functional probe to interrogate cis-regulatory remodeling, transcriptional circuitry, and apoptotic dependencies. <b>Results</b>: DNMT3B overexpression was linked to enhancer-associated chromatin activation rather than recurrent genetic mutation, particularly in CEBPA- and NPM1-mutant AML. NanA exposure produced focal epigenomic remodeling, including 6900 differentially methylated CpGs, with 268 CpGs located within regions of altered chromatin accessibility. These changes were accompanied by coordinated transcriptomic and proteomic reprogramming enriched for cell-cycle, checkpoint, and stress-response pathways. Functionally, DNMT3B perturbation induced redistribution of cell-cycle phases with increased S-phase fraction and progressive apoptosis. Transcriptional profiling demonstrated induction of BH3-only sensitizers (NOXA, PUMA), repression of BCL2, and compensatory upregulation of MCL1 and BCL-XL, collectively reshaping apoptotic dependency. Combined DNMT3B perturbation and BCL2 inhibition produced cooperative cytotoxicity in DNMT3B-high AML models. <b>Conclusion</b>: DNMT3B functions as a context-dependent epigenetic regulator linking enhancer-associated chromatin organization with proliferative control and apoptotic resistance in AML. DNMT3B-directed epigenetic perturbation remodels cis-regulatory circuitry and is associated with increased venetoclax responsiveness, supporting DNMT3B-governed networks as a candidate co-targeting axis in high-risk AML.