U6 snRNA intron insertion occurred multiple times during fungi evolution

Area of Science:

• Molecular Biology
• Genomics
• RNA Biology

Background:

• U6 small nuclear RNAs (snRNAs) are essential components of the spliceosome, crucial for RNA splicing.
• Introns are rare in structured non-coding RNAs, making their presence in U6 snRNA genes notable.

Purpose of the Study:

• To investigate the prevalence and evolutionary history of introns in fungal U6 snRNA genes.
• To analyze the characteristics and distribution of these introns across the fungal lineage.

Main Methods:

• Homology searches were performed across 147 fungal genomes to identify U6 genes.
• Comparative sequence and secondary structure analyses were conducted on identified U6 snRNA genes and their introns.

Main Results:

• U6 genes were identified in all but two of the surveyed fungal genomes.
• Intron insertion events in U6 snRNA genes are significantly more frequent in fungi than previously recognized.
• The distribution of introns suggests numerous independent insertion events throughout fungal evolution.
• Identified introns possess canonical splice and branch site motifs, indicating reliance on the spliceosomal pathway for removal.

Conclusions:

• Intron presence in U6 snRNA genes is a common phenomenon in the fungal kingdom.
• The high frequency of independent intron insertions highlights unique evolutionary dynamics of U6 snRNA in fungi.
• Fungal U6 introns are processed via the standard spliceosomal machinery.