A single m⁶A modification in U6 snRNA diversifies exon sequence at the 5' splice site

Area of Science:

• Molecular Biology
• RNA Biology
• Eukaryotic Gene Expression

Background:

• N6-methyladenosine (m6A) is a crucial RNA modification involved in various RNA metabolic processes.
• The specific functions of m6A within spliceosomal U6 small nuclear RNA (snRNA) are not well understood.

Purpose of the Study:

• To investigate the role of m6A in U6 snRNA and its impact on pre-mRNA splicing.
• To explore the evolutionary implications of m6A-mediated splicing regulation.

Main Methods:

• Large-scale transcriptome analysis of Schizosaccharomyces pombe lacking m6A modification in U6 snRNA.
• Bioinformatic analysis to identify splicing patterns and sequence enrichments.

Main Results:

• Global changes in pre-mRNA splicing were observed in the absence of U6 snRNA m6A.
• Introns significantly affected by the modification were enriched for specific sequences interacting with U6 and U5 snRNPs.
• Evidence suggests m6A facilitates the recognition of weakly interacting splice sites.

Conclusions:

• m6A in U6 snRNA plays a role in splice site recognition, likely through cooperative interactions with U5 snRNPs.
• This modification potentially relaxes constraints on 5' exon recognition, enabling greater protein sequence diversity.
• U6 snRNA m6A may have contributed to the increase in intron numbers during eukaryotic evolution.