The 18S rRNA m ⁶ A methyltransferase METTL 5 promotes mouse embryonic stem cell differentiation

Abstract

RNA modifications represent a novel layer of regulation of gene expression. Functional experiments revealed that N 6-methyladenosine (m 6 A) on messenger RNA (mRNA) plays critical roles in cell fate determination and development. m 6 A mark also resides in the decoding center of 18S ribosomal RNA (rRNA); however, the biological function of m 6 A on 18S rRNA is still poorly understood. Here, we report that methyltransferase-like 5 (METTL5) methylates 18S rRNA both in vivo and in vitro, which is consistent with previous reports. Deletion of Mettl5 causes a dramatic differentiation defect in mouse embryonic stem cells (mESCs). Mechanistically, the m 6 A deposited by METTL5 is involved in regulating the efficient translation of F-box and WD repeat domain-containing 7 (FBXW7), a key regulator of cell differentiation. Deficiency of METTL5 reduces FBXW7 levels and leads to the accumulation of its substrate c-MYC, thereby delaying the onset of mESC differentiation. Our study uncovers an important role of METTL5-mediated 18S m 6 A in mESC differentiation through translation regulation and provides new insight into the functional significance of rRNA m 6 A.

Regulation of Ribosome Function by RNA Modifications in Hematopoietic Development and Leukemia: It Is Not Only a Matter of m6A

“…Notably, the knockdown of Ddx21 phenocopies the depletion of Aes by reducing growth capacity of leukemia cells [23]. Other modifications in rRNAs, such as m 6 A and m 5 C, have been recently linked to ribosome function, stem cell differentiation, and cancer [27][28][29][64][65][66][67]. In particular, 18S and 28S rRNAs contain two m 6 A methylations at position A1832 and A4220, respectively.…”

“…However, both studies found that METTL5 was required for correct differentiation. Furthermore, the lack of m 6 A in 18S rRNA was found to affect the translation of specific mRNAs [28]. Translation of Fbxw7 (F-box and WD repeat domain-containing protein 7), a protein involved in the degradation of c-MYC, was found to be specifically regulated by 18S rRNA m 6 A modification and to play an important role in mESC differentiation [28].…”

“…Furthermore, the lack of m 6 A in 18S rRNA was found to affect the translation of specific mRNAs [28]. Translation of Fbxw7 (F-box and WD repeat domain-containing protein 7), a protein involved in the degradation of c-MYC, was found to be specifically regulated by 18S rRNA m 6 A modification and to play an important role in mESC differentiation [28]. Restoring Fbxw7 expression compensated for the cell differentiation defect due to Mettl5 depletion [28].…”

“…Translation of Fbxw7 (F-box and WD repeat domain-containing protein 7), a protein involved in the degradation of c-MYC, was found to be specifically regulated by 18S rRNA m 6 A modification and to play an important role in mESC differentiation [28]. Restoring Fbxw7 expression compensated for the cell differentiation defect due to Mettl5 depletion [28]. Notably, deregulation of FBXW7 expression is connected to the development of different types of leu- An additional chemical modification with a role in hematopoietic development is the N 1 -methyladenosine (m 1 A) at position A 1309 and A 1136 in human and mouse 28S rRNA, respectively, which is required for the production of mature 60S ribosomal subunits [25].…”

Enzymatic characterization of three human RNA adenosine methyltransferases reveals diverse substrate affinities and reaction optima

“…MettL5 forms a heterodimer with Trm112, a conserved protein that binds to and stabilizes various MTase proteins and was named initially for its role in tR NA m ethylation ( 29 , 30 ). The MettL5-Trm112 complex is responsible for 18S rRNA adenine methylation at position 1832 ( 31 , 32 , 33 , 34 , 35 ). Finally, MettL16 catalyzes adenine methylation in the conserved sequence UAC A GAGAA, within hairpins in the 3′ UTR of the SAM synthetase (MAT2A) mRNA and in U6 snRNA ( 36 , 37 , 38 ).…”