Published on None in volume (2018) Mol Cell 71: 986-1000.e11 .

PubMed ID: 30197299 

DOI: 10.1016/j.molcel.2018.08.004

Abstract:

Internal modification of RNAs with N 6 -methyladenosine (m 6 A) is a highly conserved means of gene expression control. While the METTL3/METTL14 heterodimer adds this mark on thousands of transcripts in a single-stranded context, the substrate requirements and physiological roles of the second m 6 A writer METTL16 remain unknown. Here we describe the crystal structure of human METTL16 to reveal a methyltransferase domain furnished with an extra N-terminal module, which together form a deep-cut groove that is essential for RNA binding. When presented with a random pool of RNAs, METTL16 selects for methylation-structured RNAs where the critical adenosine is present in a bulge. Mouse 16-cell embryos lacking Mettl16 display reduced mRNA levels of its methylation target, the SAM synthetase Mat2a. The consequence is massive transcriptome dysregulation in ∼64-cell blastocysts that are unfit for further development. This highlights the role of an m 6 A RNA methyltransferase in facilitating early development via regulation of SAM availability.