An Archaeal RNA Methyltransferase Generates N2,7-Dimethylguanosine at Ribosomal A Site

ABSTRACT: N2,7-dimethylguanosine (m2,7G) and N2,2,7-trimethylguanosine (m2,2,7G) are post‑transcriptional modifications of the RNA 5′ cap present in eukaryotes and some RNA viruses catalyzedby trimethylguanosine synthases (TGS). TGS typically requires m7G as a substrate for guanine-N2 mono- or dimethylation. These enzymes play critical roles in the transport and maturation of ribonucleoprotein complexes and are implicated in viral protein synthesis. In this study, we describe a guanine-N2,7 methyltransferase encoded by the TK0807 gene of Thermococcus kodakarensis that independently converts guanosine into m2,7G within the conserved helix 18 of the archaeal 16S rRNA. Biochemical characterization of recombinant TK0807 reveals this methyltransferase can sequentially produce m2,7G via an m7G intermediate, and that activity depends on a structurally defined substrate sustained through intramolecular base pairing. A 2.1 Å co-crystal structure of TK0807 bound to a synthetic oligonucleotide and S-adenosylhomocysteine shows the target guanosine adopting a syn conformation within the catalytic site, providing molecular insights into substrate recognition and catalysis. Finally, homologs capable of synthesizing m2,7G were also identified in Pyrococcus abyssi and Archaeoglobus veneficus, unveiling an evolutionarily common RNA dual methylation strategy in thermophilic archaea, which is mediated by a highly specific guanine-N2,7 methyltransferase and has not been described in any domain of life.

INSTRUMENT(S):

ORGANISM(S): Thermococcus Kodakarensis

SUBMITTER: Yueh-Lin Tsai  

LAB HEAD: Ivan R. Corrêa Jr.

PROVIDER: PXD084674 | Pride | 2026-10-09

REPOSITORIES: Pride