Functional heritage: the evolution of chimeric RNA into a gene

Area of Science:

• Molecular Biology
• Genomics
• Evolutionary Biology

Background:

• Chimeric RNAs were once thought to be exclusive to neoplasia but are now recognized in normal physiological processes.
• The hypothesis posits that chimeric RNAs might serve as functional precursors to genes, acting as a transitional mechanism before genomic fixation.

Purpose of the Study:

• To investigate the potential functional role of chimeric RNAs as gene precursors.
• To explore the evolutionary relationship between the chimeric RNA HNRNPA1L2-SUGT1 (H-S) and the putative pseudogene MRPS31P5.

Main Methods:

• Sequence analysis comparing H-S chimera, MRPS31P5, and MRPS31.
• Bioinformatic and experimental detection of H-S in marmosets.
• Gene silencing experiments in marmoset and human cell lines.
• Whole transcriptome analysis and downstream target validation.

Main Results:

• MRPS31P5 transcript shows higher similarity to H-S chimera than to its parent gene MRPS31.
• H-S chimera is evolutionarily older than MRPS31P5, detected in marmosets lacking MRPS31P5.
• Silencing H-S in marmosets phenocopies MRPS31P5 silencing in humans, indicating shared functional pathways.
• MRPS31P5 partially rescues H-S silencing, suggesting MRPS31P5 evolved from H-S.

Conclusions:

• MRPS31P5 is likely a functional descendant of the H-S chimera, not a true pseudogene of MRPS31.
• The H-S chimera arises from cis-splicing, while MRPS31P5 is likely generated by genome rearrangement.
• This study provides evidence for chimeric RNAs as precursors in gene evolution.