Evolutionary origin of the U6 small nuclear RNA intron

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genetics

Background:

• U6 small nuclear RNA is crucial for pre-mRNA splicing and highly conserved across species.
• The U6 gene in Schizosaccharomyces pombe is known to contain an intron.
• Introns in U6 genes are rare, making their presence in some species noteworthy.

Purpose of the Study:

• To investigate the presence and conservation of introns in U6 genes across different Schizosaccharomyces species.
• To compare the U6 gene structure in Schizosaccharomyces with other fungal and distantly related organisms.
• To infer the evolutionary origin of the intron in the U6 gene.

Main Methods:

• Comparative analysis of U6 gene sequences from four Schizosaccharomyces species.
• Sequence comparison with U6 genes from ascomycete, basidiomycete fungi, and other organisms.
• Phylogenetic analysis to determine intron insertion events.

Main Results:

• All four analyzed Schizosaccharomyces species possess a U6 gene interrupted by a homologous intron at the identical position.
• In contrast, U6 genes from ascomycete, basidiomycete fungi, and other examined groups are colinear (lack introns).
• The intron's presence is specific to the Schizosaccharomyces genus within the studied groups.

Conclusions:

• The data strongly suggest that the ancestral U6 gene was intronless.
• The intron in the Schizosaccharomyces U6 gene was acquired through a single, relatively recent insertional event.
• This finding provides insights into the dynamic evolution of gene structure and intron acquisition.