Figure 5. METT‐10 catalyzes m⁶A modification at the invariant AG dinucleotide of the distal 3′SS in␣vitro .

• A
  Mass chromatograms of RNA fragments to detect m⁶A (top) or unmodified A (bottom) after in␣vitro incubation of 127‐nt sams‐3/sams‐4 pre‐mRNA (sequence available in Fig EV2) with recombinant full‐length METT‐10 protein in the presence (left) or absence (right) of 1 mM SAM. The sequence, m/z value, and charge state for each fragment are indicated on the right. Asterisks indicate non‐specific signals.
• B
  The negatively charged ions of RNase T1 fragment is decomposed in the instrument by collision‐induced dissociation (CID) using helium gas. The product ions produced by CID are assigned on the sequence illustrated on the top right inset panel. Nomenclature of the product ions are described in the literature (McLuckey et␣al, 1992). Product ions of c and y series derive from the 5′ and 3′ termini of the fragment, respectively.