Poster abstracts
Poster number 125 submitted by Agnieszka Ruszkowska
Structural insights into the RNA methyltransferase domain of METTL16
Agnieszka Ruszkowska (Department of Chemistry and Biochemistry, University of Notre Dame), Milosz Ruszkowski (Synchrotron Radiation Research Section of MCL, National Cancer Institute), Zbigniew Dauter (Synchrotron Radiation Research Section of MCL, National Cancer Institute), Jessica A. Brown (Department of Chemistry and Biochemistry, University of Notre Dame)
Abstract:
N6-methyladenosine (m6A) is an RNA modification that plays a central role in biology. Most m6A marks are catalyzed by a heterodimeric complex comprised of methyltransferase-like protein 3 and methyltransferase-like protein 14 (METTL3/METTL14), which specifically methylates adenine within a RRACH (R = A or G; H = A, C, or U) sequence motif. Recently, methyltransferase-like protein 16 (METTL16) was confirmed to be an m6A RNA methyltransferase that modifies U6 spliceosomal RNA and the MAT2A mRNA encoding S-adenosylmethionine (SAM) synthase. Unlike METTL3/METTL14, METTL16-dependent m6A marks do not occur within the RRACH sequence motif, and they are found in introns and at intron-exon boundaries. Multiple studies report that METTL16 uses a combination of sequence and structure to recognize its RNA substrates and binding partners, some of which are implicated in cancer. For example, METTL16 interacts with an RNA triple helix located at the 3' end of the long non-coding RNA, MALAT1 (metastasis-associated lung adenocarcinoma transcript 1). METTL16 binding depends on both the nucleotide composition and structure of the MALAT1 triple helix.
Here, we present two X-ray crystal structures of the N-terminal methyltransferase domain (residues 1-291) of human METTL16 (METTL16_291): an apo structure at 1.9 Å resolution and S-adenosylhomocysteine-bound complex at 2.1 Å resolution. The structures revealed a highly conserved Rossmann fold that is characteristic of Class I S-adenosylmethionine-dependent methyltransferases and a large, positively charged groove which represents the RNA-binding site. In-depth analysis of the active site led to a model of the methyl transfer reaction catalyzed by METTL16. A native gel-shift assay shows that in contrast to full-length METTL16, METTL16_291 does not bind to the MALAT1 triple helix. Our results provide insights into the molecular structure of METTL16, which is distinct from METTL3/METTL14.
Keywords: METTL16, RNA methyltransferase , N6-methyladenosine