5-methylcytosine promotes mRNA export — NSUN2 as the methyltransferase and ALYREF as an m5C reader

Abstract

5-methylcytosine (m5C) is a post-transcriptional RNA modification identified in both stable and highly abundant tRNAs and rRNAs, and in mRNAs. However, its regulatory role in mRNA metabolism is still largely unknown. Here, we reveal that m5C modification is enriched in CG-rich regions and in regions immediately downstream of translation initiation sites and has conserved, tissue-specific and dynamic features across mammalian transcriptomes. Moreover, m5C formation in mRNAs is mainly catalyzed by the RNA methyltransferase NSUN2, and m5C is specifically recognized by the mRNA export adaptor ALYREF as shown by in vitro and in vivo studies. NSUN2 modulates ALYREF's nuclear-cytoplasmic shuttling, RNA-binding affinity and associated mRNA export. Dysregulation of ALYREF-mediated mRNA export upon NSUN2 depletion could be restored by reconstitution of wild-type but not methyltransferase-defective NSUN2. Our study provides comprehensive m5C profiles of mammalian transcriptomes and suggests an essential role for m5C modification in mRNA export and post-transcriptional regulation.

5-methylcytosine mediates nuclear export of mRNA

“…The extensive study by Yang et al in May issue of Cell Research significantly upgrades the standing of m 5 C in the epitranscriptome field [7]. The detailed unique m 5 C topology, as explored in this study, differs from that reported before.…”

ALY RNA-Binding Proteins Are Required for Nucleocytosolic mRNA Transport and Modulate Plant Growth and Development

“…First, we compared the amino acid sequences of the four Arabidopsis ALY proteins (ALY1- modification of mRNAs and other RNAs in Arabidopsis (David et al 2017) and that 175 mammalian ALY preferentially binds to m 5 C-modified RNA (Yang et al 2017). Therefore,…”

“…Like mammalian ALY (Yang et al 2017), Arabidopsis ALY1 396 exhibits a significantly higher affinity for m 5 C-modified RNA. The m 5 C modification is mammals (Yang et al 2017), a mechanism that may be conserved in plants (David et al 399 2017). whereas the other ALY proteins were also expressed in the surrounding sporophytic tissues.…”

“…In 386 another EMSA study, the minimal RNA-binding site was mapped to a stretch of 21 amino 387 acid residues within the variable N-terminal domain of murine ALY (Hautbergue et al 2008), (Heath et al 2016). Like mammalian ALY (Yang et al 2017), Arabidopsis ALY1 396 exhibits a significantly higher affinity for m 5 C-modified RNA. The m 5 C modification is mammals (Yang et al 2017), a mechanism that may be conserved in plants (David et al 399 2017).…”

Synthesis and Multiple Incorporations of 2′‐O‐Methyl‐5‐hydroxymethylcytidine, 5‐Hydroxymethylcytidine and 5‐Formylcytidine Monomers into RNA Oligonucleotides

“…[6, 7] Additionally, it is proposed that m 5 C is essential for mRNA export and post-transcriptional regulation. [8] Significant enrichment of hm 5 C in polyadenylated RNA compared to total RNA further suggests that biosynthesis of hm 5 C might be a part of a dynamic regulatory mechanism of RNA. [6b, 9] The f 5 C modification is prevalent at the wobble position of an anticodon loop of mitochondrial methionine tRNA in many species, including humans.…”