Two RNA-binding sites in plant fibrillarin provide interactions with various RNA substrates

Area of Science:

• Molecular Biology
• Plant Science
• Virology

Background:

• Fibrillarin is a key nucleolar protein essential for ribosome biogenesis.
• Fibrillarin has been implicated in viral infections and association with viral ribonucleoprotein complexes.

Purpose of the Study:

• To investigate the RNA-binding capabilities of recombinant Arabidopsis thaliana fibrillarin 2 (AtFib2).
• To identify the specific regions within AtFib2 responsible for RNA interaction.

Main Methods:

• In vitro RNA-binding assays using recombinant AtFib2.
• Analysis of RNA-binding specificity across different RNA types and lengths.
• Protein domain mapping to identify RNA-binding sites.

Main Results:

• AtFib2 demonstrated binding to various RNA molecules, including ribosomal RNA (rRNA), small nucleolar RNA (snoRNA), small nuclear RNA (snRNA), small interfering RNA (siRNA), and viral RNAs.
• Two distinct RNA-binding sites were identified within AtFib2: one in the central region (amino acids 138-179) and another in the C-terminal region (amino acids 225-281).
• The conserved GCVYAVEF octamer motif was found not to directly bind RNA but likely contributes to the proper folding of the central RNA-binding site.

Conclusions:

• Arabidopsis fibrillarin 2 exhibits broad RNA-binding activity in vitro.
• The identified RNA-binding sites in AtFib2 are critical for its interactions with diverse RNA molecules, potentially including viral RNAs.
• These findings enhance our understanding of fibrillarin's role in RNA metabolism and viral pathogenesis.