8pwb
Crystal structure of the human METTL3-METTL14 in complex with a bisubstrate analogue (BA6)
Structural highlights
FunctionMTA70_HUMAN N6-methyltransferase that methylates adenosine residues of some RNAs and acts as a regulator of the circadian clock, differentiation of embryonic stem cells and primary miRNA processing. N6-methyladenosine (m6A), which takes place at the 5'-[AG]GAC-3' consensus sites of some mRNAs, plays a role in the efficiency of mRNA splicing, processing, translation efficiency, editing and mRNA stability (PubMed:22575960, PubMed:24284625, PubMed:25719671, PubMed:25799998, PubMed:26321680, PubMed:26593424, PubMed:9409616). M6A regulates the length of the circadian clock: acts as a early pace-setter in the circadian loop by putting mRNA production on a fast-track for facilitating nuclear processing, thereby providing an early point of control in setting the dynamics of the feedback loop (By similarity). M6A also acts as a regulator of mRNA stability: in embryonic stem cells (ESCs), m6A methylation of mRNAs encoding key naive pluripotency-promoting transcripts results in transcript destabilization, promoting differentiation of ESCs (By similarity). M6A also takes place in other RNA molecules, such as primary miRNA (pri-miRNAs) (PubMed:25799998). Mediates methylation of pri-miRNAs, marking them for recognition and processing by DGCR8 (PubMed:25799998).[UniProtKB:Q8C3P7][1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedThe complex of methyltransferase-like proteins 3 and 14 (METTL3-14) is the major enzyme that deposits N(6)-methyladenosine (m(6)A) modifications on messenger RNA (mRNA) in humans. METTL3-14 plays key roles in various biological processes through its methyltransferase (MTase) activity. However, little is known about its substrate recognition and methyl transfer mechanism from its cofactor and methyl donor S-adenosylmethionine (SAM). Here, we study the MTase mechanism of METTL3-14 by a combined experimental and multiscale simulation approach using bisubstrate analogues (BAs), conjugates of a SAM-like moiety connected to the N(6)-atom of adenosine. Molecular dynamics simulations based on crystal structures of METTL3-14 with BAs suggest that the Y406 side chain of METTL3 is involved in the recruitment of adenosine and release of m(6)A. A crystal structure with a BA representing the transition state of methyl transfer shows a direct involvement of the METTL3 side chains E481 and K513 in adenosine binding which is supported by mutational analysis. Quantum mechanics/molecular mechanics (QM/MM) free energy calculations indicate that methyl transfer occurs without prior deprotonation of adenosine-N(6). Furthermore, the QM/MM calculations provide further support for the role of electrostatic contributions of E481 and K513 to catalysis. The multidisciplinary approach used here sheds light on the (co)substrate binding mechanism, catalytic step, and (co)product release, and suggests that the latter step is rate-limiting for METTL3. The atomistic information on the substrate binding and methyl transfer reaction of METTL3 can be useful for understanding the mechanisms of other RNA MTases and for the design of transition state analogues as their inhibitors. The catalytic mechanism of the RNA methyltransferase METTL3.,Corbeski I, Vargas-Rosales PA, Bedi RK, Deng J, Coelho D, Braud E, Iannazzo L, Li Y, Huang D, Etheve-Quelquejeu M, Cui Q, Caflisch A Elife. 2024 Mar 12;12:RP92537. doi: 10.7554/eLife.92537. PMID:38470714[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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