N 6-methyladenosine (m6A) is the most prevalent modification in eukaryotic messenger RNAs (mRNAs) and is interpreted by its readers, such as YTH domain-containing proteins, to regulate mRNA fate. Here we report the insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs; including IGF2BP1/2/3) as a distinct family of m6A readers that target thousands of mRNA transcripts through recognizing the consensus GG(m6A)C sequence. In contrast to the mRNA-decay-promoting function of YTHDF2, IGF2BPs promote the stability and storage of their target mRNAs (e.g., MYC) in an m6A-depedent manner under normal and stress conditions and thus affect gene expression output. Moreover, the K homology (KH) domains of IGF2BPs are required for their recognition of m6A and are critical for their oncogenic functions. Our work therefore reveals a different facet of the m6A-reading process that promotes mRNA stability and translation, and highlights the functional importance of IGF2BPs as m6A readers in post-transcriptional gene regulation and cancer biology.

R-2-hydroxyglutarate (R-2HG), produced at high levels by mutant isocitrate dehydrogenase 1/2 (IDH1/2) enzymes, was reported as an oncometabolite. We show here that R-2HG also exerts a broad anti-leukemic activity in vitro and in vivo by inhibiting leukemia cell proliferation/viability and by promoting cell-cycle arrest and apoptosis. Mechanistically, R-2HG inhibits fat mass and obesity-associated protein (FTO) activity, thereby increasing global N-methyladenosine (mA) RNA modification in R-2HG-sensitive leukemia cells, which in turn decreases the stability of MYC/CEBPA transcripts, leading to the suppression of relevant pathways. Ectopically expressed mutant IDH1 and S-2HG recapitulate the effects of R-2HG. High levels of FTO sensitize leukemic cells to R-2HG, whereas hyperactivation of MYC signaling confers resistance that can be reversed by the inhibition of MYC signaling. R-2HG also displays anti-tumor activity in glioma. Collectively, while R-2HG accumulated in IDH1/2 mutant cancers contributes to cancer initiation, our work demonstrates anti-tumor effects of 2HG in inhibiting proliferation/survival of FTO-high cancer cells via targeting FTO/mA/MYC/CEBPA signaling.

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.

N6-methyladenosine (m6A), the most abundant internal modification in eukaryotic messenger RNAs (mRNAs), has been shown to play critical roles in various normal bioprocesses such as tissue development, stem cell self-renewal and differentiation, heat shock or DNA damage response, and maternal-to-zygotic transition. The m6A modification is deposited by the m6A methyltransferase complex (MTC; i.e., writer) composed of METTL3, METTL14 and WTAP, and probably also VIRMA and RBM15, and can be removed by m6A demethylases (i.e., erasers) such as FTO and ALKBH5. The fates of m6A-modified mRNAs rely on the functions of distinct proteins that recognize them (i.e., readers), which may affect the stability, splicing, and/or translation of target mRNAs. Given the functional importance of the m6A modification machinery in normal bioprocesses, it is not surprising that evidence is emerging that dysregulation of m6A modification and the associated proteins also contributes to the initiation, progression, and drug response of cancers. In this review, we focus on recent advances in the study of biological functions and the underlying molecular mechanisms of dysregulated m6A modification and the associated machinery in the pathogenesis and drug response of various types of cancers. In addition, we also discuss possible therapeutic interventions against the dysregulated m6A machinery to treat cancers.

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

As the most abundant internal modification in eukaryotic messenger RNAs identified, N-methyladenosine (mA) has been shown recently to play essential roles in various normal bioprocesses. Evidence is emerging that mA modification and its regulatory proteins also play critical roles in various cancers including leukemia, brain tumor, breast cancer and lung cancer, etc. For instance, FTO, the first mA demethylase identified, has been reported recently to play an oncogenic role in leukemia and glioblastoma. ALKBH5 (another mA demethylase) has been reported to exert a tumor-promoting function in glioblastoma and breast cancer. METTL3 (a major mA methyltransferase) likely plays distinct roles between glioblastoma and lung cancer. Here we discuss the recent progress and future prospects in study of mA machinery in cancer.