Intrinsically disordered RNA-binding motifs cooperate to catalyze RNA folding and drive phase separation

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• RNA-binding proteins are crucial for gene regulation and cellular organization.
• The yeast protein Loc1p is involved in ribosome biogenesis.

Purpose of the Study:

• To characterize the RNA-binding properties of Loc1p.
• To investigate the function of novel positively charged, unstructured nucleic acid binding (PUN) motifs.

Main Methods:

• Biochemical analysis of Loc1p and its PUN motifs.
• RNA binding and folding assays.
• Proteome-wide searches for PUN motif-containing proteins.

Main Results:

• Loc1p is an intrinsically disordered RNA-binding protein featuring eight repeating PUN motifs.
• A single PUN motif stabilizes folded RNAs, while multiple motifs cooperatively catalyze RNA folding.
• Multivalent PUN motifs drive RNA-induced phase separation.
• Proteome-wide searches revealed enrichment of PUN motifs in proteins involved in RNA and DNA remodeling.

Conclusions:

• PUN motifs are key functional units for RNA folding and phase separation.
• These motifs are widespread across species and likely involved in diverse RNA- and DNA-related cellular processes.
• PUN motifs may have played a role in the folding of early ribozymes in an ancient 'RNA world'.