RNA N -Methyladenosine Modification in Normal and Malignant Hematopoiesis.

As the most abundant internal modification in eukaryotic messenger RNAs (mRNAs), N -methyladenosine (mA) modification has been shown recently to posttranscriptionally regulate expression of thousands of messenger RNA (mRNA) transcripts in each mammalian cell type in a dynamic and reversible manner. This epigenetic mark is deposited by the mA methyltransferase complex (i.e., the METTL3/METTL14/WTAP complex and other cofactor proteins) and erased by mA demethylases such as FTO and ALKBH5. Specific recognition of these mA-modified mRNAs by mA-binding proteins (i.e., mA readers) determines the fate of target mRNAs through affecting splicing, nuclear export, RNA stability, and/or translation. During the past few years, mA modification has been demonstrated to play a critical role in many major normal bioprocesses including self-renewal and differentiation of embryonic stem cells and hematopoietic stem cells, tissue development, circadian rhythm, heat shock or DNA damage response, and sex determination. Thus, it is not surprising that dysregulation of the mA machinery is also closely associated with pathogenesis and drug response of both solid tumors and hematologic malignancies. In this chapter, we summarize and discuss recent findings regarding the biological functions and underlying mechanisms of mA modification and the associated machinery in normal hematopoiesis and the initiation, progression, and drug response of acute myeloid leukemia (AML), a major subtype of leukemia usually associated with unfavorable prognosis.