RNA-binding proteins are essential for gene regulation and the spatial organization of cells. We report that the yeast ribosome biogenesis factor Loc1p is an intrinsically disordered RNA-binding protein with eight repeating positively charged, unstructured nucleic acid binding (PUN) motifs. While a single of these previously undefined motifs stabilizes folded RNAs, multiple copies strongly cooperate to catalyze RNA folding. In the presence of RNA, these multivalent PUN motifs drive phase separation. Proteome-wide searches in pro- and eukaryotes for proteins with arrays of PUN motifs reveal a strong enrichment in RNA-mediated processes and DNA remodeling events. Thus, PUN motifs appear to be involved in a large variety of RNA- and DNA-related processes by concentrating them into membrane-less organelles. The wide distribution of PUN motifs in all kingdoms of life suggests that in an ancient “RNA world” such PUN-like motifs might have advanced the co-evolution of early ribozymes with peptides of growing size, thereby promoting the transition into a protein-dominated world.
the bioinformatic analyses to define PUN proteins globally in 5 different Organisms. Code is ordered by organism.