Figure 4.

m¹A accumulates in SGs. (A) Extracted ion chromatograms of indicated m/z with a range of ±0.002 Da. Top, a mixture of four standard ribonucleosides plus N1-methyladenosine and N6-methyladenosine; middle, N6-methyadenosine only; bottom, N1-methyladenosine only. A, adenosine. *, Dimroth rearrangement of m¹A to m⁶A. (B) The fraction of methylated adenine in SG RNAs (SG) is increased compared to that in the cytosolic mRNA pool (cytosol) as measured by selective ion monitoring MS. **P < 0.01, two-tailed t-test. N = 3 independent experiments (mean + SD). (C) m¹A enriched in SG RNA is stronger than m⁶A. m¹A, fraction of N1-methyladenosine over unmodified adenosine; m⁶A, fraction of N6-methyladenosine over unmodified adenosine. The fractions of m¹A and m⁶A in cytosolic mRNAs were set as 1. ***P < 0.001, two-tailed t-test; N = 3 independent experiments (mean + SD).