Spliceosomal intronogenesis

Area of Science:

• Molecular Biology
• Genomics
• Evolutionary Biology

Background:

• Introns, intervening sequences in eukaryotic nuclear genomes, are essential for mRNA processing via the spliceosome.
• While intron loss is experimentally verified, intron gain mechanisms and evidence have remained largely theoretical, primarily suggested by phylogenetic analyses.
• Understanding intron dynamics is crucial for comprehending genome evolution and gene regulation.

Purpose of the Study:

• To develop and utilize a strategy for detecting intron gain and loss events experimentally.
• To provide the first experimental verification of intron transposition (gain) in any organism.
• To investigate the functionality of newly acquired introns and their target genes.

Main Methods:

• A screening strategy was employed to detect intron gain and loss events.
• Reporter introns were used to track transposition events into specific yeast genes.
• Functional analysis of genes with newly acquired introns was performed, including spliceosome-mediated removal and gene expression studies.

Main Results:

• The study experimentally verified two instances of intron gain through the transposition of a reporter intron into the yeast genes RPL8B and ADH2.
• The newly integrated introns were successfully recognized and removed by the spliceosome from their respective pre-mRNAs.
• The RPL8B gene with the new intron (RPL8Bint) was found to be functional when overexpressed in a relevant yeast strain.

Conclusions:

• This research presents the first experimental evidence of intron transposition, a novel mechanism for intron gain.
• The findings demonstrate that newly acquired introns can be functional and integrated into cellular processes, including splicing.
• The study opens new avenues for investigating intron origin, propagation, and their role in shaping eukaryotic genomes.