N-methyladenosine (mA), the most prevalent internal modification in eukaryotic messenger RNAs (mRNAs), plays critical roles in many bioprocesses. However, its functions in normal and malignant hematopoiesis remain elusive. Here, we report that METTL14, a key component of the mA methyltransferase complex, is highly expressed in normal hematopoietic stem/progenitor cells (HSPCs) and acute myeloid leukemia (AML) cells carrying t(11q23), t(15;17), or t(8;21) and is downregulated during myeloid differentiation. Silencing of METTL14 promotes terminal myeloid differentiation of normal HSPCs and AML cells and inhibits AML cell survival/proliferation. METTL14 is required for development and maintenance of AML and self-renewal of leukemia stem/initiation cells (LSCs/LICs). Mechanistically, METTL14 exerts its oncogenic role by regulating its mRNA targets (e.g., MYB and MYC) through mA modification, while the protein itself is negatively regulated by SPI1. Collectively, our results reveal the SPI1-METTL14-MYB/MYC signaling axis in myelopoiesis and leukemogenesis and highlight the critical roles of METTL14 and mA modification in normal and malignant hematopoiesis.

DNA and histone modifications exhibit noticeable impacts on gene expression 1 . Being the most prevalent internal modification in mRNA, N 6 -Methyladenosine (m 6 A) mRNA modification emerges as an important post-transcriptional mechanism of gene regulation 2 - 4 and plays critical roles in various normal and pathological bioprocesses 5 - 12 . However, how m 6 A is precisely and dynamically deposited in the transcriptome remains elusive. Here we report that H3K36me3 histone modification, a marker for transcription elongation, globally guides m 6 A modification. We found that m 6 A modifications enrich in the vicinity of H3K36me3 peaks, and are reduced globally when cellular H3K36me3 is depleted. Mechanistically, H3K36me3 is recognized and bound directly by METTL14, a critical component of the m 6 A methyltransferase complex (MTC), which in turn facilitates the binding of the m 6 A MTC to adjacent RNA polymerase II, and thereby delivering the m 6 A MTC to actively transcribed nascent RNAs to deposit m 6 A co-transcriptionally. In mouse embryonic stem cells, phenocopying Mettl14 silencing, H3K36me3 depletion also induces m 6 A reduction transcriptome-wide and in pluripotency transcripts, resulting in increased cell stemness. Collectively, our studies reveal the critical roles of H3K36me3 and METTL14 in determining precise and dynamic m 6 A deposition in mRNA, and uncover another layer of gene expression regulation involving crosstalk between histone modification and RNA methylation.

Highlights d Development of two potent FTO inhibitors with IC 50 values in the low nanomolar range d KD of FTO or pharmacological inhibition of FTO suppresses LSC/LIC self-renewal d Targeting FTO suppresses immune checkpoint gene expression and immune evasion d Targeting FTO by potent inhibitors holds therapeutic promise against various cancers

Highlights d ALKBH5 is overexpressed in AML, which correlates with poor prognosis in patients d ALKBH5 is required for the development and progression of AML d ALKBH5 is essential for LSC/LIC self-renewal, but not normal hematopoiesis d The ALKBH5/m 6 A/TACC3 axis contributes to the functions of ALKBH5 in AML