The N ⁶-methyladenosine (m ⁶A)-forming enzyme METTL3 controls myeloid differentiation of normal and leukemia cells

Abstract

N ⁶-methyladenosine (m ⁶A) is an abundant nucleotide modification in mRNA that is required for the differentiation of mouse embryonic stem cells. However, it remains unknown whether m ⁶A controls differentiation of normal and/or malignant myeloid hematopoietic cells. Here we show that shRNA-mediated depletion of the m ⁶A-forming enzyme METTL3 in human hematopoietic stem/progenitor cells promotes differentiation coupled with reduced proliferation. Conversely, overexpression of wild-type METTL3, but not the catalytic-dead form of METTL3, inhibits differentiation and increases cell growth. METTL3 mRNA and protein is expressed more abundantly in acute myeloid leukemia (AML) cells compared to healthy hematopoietic stem/progenitor cells and other types of tumors. Furthermore, METTL3 depletion in humanmyeloid leukemia cell lines induces differentiation and apoptosis and delays leukemia in recipient mice in vivo. Single-nucleotide resolution mapping of m ⁶A coupled with ribosome profiling reveals that m ⁶A promotes the translation of c-MYC, BCL2 and PTEN mRNAs in human myeloid leukemia MOLM13 cells. Moreover, loss of METTL3 leads to increased levels of pAKT, which contributes to the differentiation effects of METTL3 depletion. Overall these results provide a rationale for therapeutic targeting of METTL3 in myeloid leukemia.