Decoding m⁶Am by simultaneous transcription-start mapping and methylation quantification

Area of Science:

• Molecular Biology
• Epigenetics
• RNA Biology

Background:

• N6,2"-O-dimethyladenosine (m6Am) is a crucial epitranscriptomic modification found at the 5"-end of mRNA and snRNA.
• Current m6Am detection methods are limited by the assumption of single transcription start sites per gene, failing to account for transcript isoform diversity.

Purpose of the Study:

• To develop and apply a novel method, CROWN-seq, for simultaneous identification of transcription start sites and quantification of m6Am stoichiometry across diverse RNA isoforms.
• To comprehensively map the m6Am landscape in human cells and investigate its relationship with transcript expression and transcription initiation.

Main Methods:

• CROWN-seq: A novel technique designed to identify transcription start nucleotides and quantify m6Am stoichiometry for adenosine-initiated 5"-isoforms.
• Application of CROWN-seq across nine human cell lines to generate a detailed m6Am landscape.

Main Results:

• m6Am modification is predominantly a high-stoichiometry event across the transcriptome, with exceptions in a small fraction of mRNAs.
• m6Am modification is positively correlated with increased transcript expression levels.
• Evidence suggests a link between m6Am and transcription initiation, potentially involving specific promoter sequences and mechanisms.

Conclusions:

• CROWN-seq provides unprecedented resolution for mapping m6Am modifications across transcript isoforms.
• m6Am plays a significant role in regulating gene expression, potentially influencing transcription initiation.
• These findings open new avenues for understanding the functional impact of m6Am in RNA biology and gene regulation.