m¹A within cytoplasmic mRNAs at single nucleotide resolution: a reconciled transcriptome-wide map

Area of Science:

• Molecular Biology
• RNA Biology
• Epigenetics

Background:

• Over 100 chemical modifications exist for RNA.
• Recent studies developed methods to map N1-methyladenosine (m¹A) at single nucleotide resolution.
• Conflicting results emerged regarding m¹A abundance and localization in cytosolic mRNAs.

Purpose of the Study:

• To reanalyze data from a previous study on m¹A mapping.
• To reconcile discrepancies in m¹A site identification and stoichiometry.
• To provide a clear understanding of m¹A modification in cytosolic mRNAs.

Main Methods:

• Reanalysis of existing m¹A mapping data.
• Identification and filtering of artifacts including duplications, misannotations, and sequencing errors.
• Comparison with data from a parallel study.

Main Results:

• The majority of previously reported m¹A sites were identified as artifacts.
• Only 53 bona fide internal m¹A sites were confirmed in cytosolic mRNAs.
• These confirmed sites are typically low abundance and likely TRMT6/TRMT61A substrates.

Conclusions:

• m¹A is a rare internal modification in cytosolic mRNAs.
• Previous high-abundance estimates were largely due to data artifacts.
• Consistent data indicate m¹A is scarce and low stoichiometry, primarily mediated by TRMT6/TRMT61A.