Evolution of RNA-Protein Interactions: Non-Specific Binding Led to RNA Splicing Activity of Fungal Mitochondrial Tyrosyl-tRNA Synthetases
Year: 2014
Type: article
Abstract: The Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (mtTyrRS; CYT-18 protein) evolved a new function as a group I intron splicing factor by acquiring the ability to bind group I intron RNAs and stabilize their catalytically active RNA structure. Previous studies showed: (i) CYT-18 binds group I introns by using both its N-terminal catalytic domain and flexibly attached C-terminal anticodon-binding domain (CTD); and (ii) the catalytic domain binds group I introns specifically via multiple structural adaptations that occurred during or after the divergence of Peziomycotina and Saccharomycotina. However, the function of the CTD and how it contributed to the evolution of splicing activity have been unclear. Here, small angle X-ray scattering analysis of CYT-18 shows that both CTDs of the homodimeric protein extend outward from the catalytic domain, but move inward to bind opposite ends of a group I intron RNA. Biochemical assays show that the isolated CTD of CYT-18 binds RNAs non-specifically, possibly contributing to its interaction with the structurally different ends of the intron RNA. Finally, we find that the yeast mtTyrRS, which diverged from Pezizomycotina fungal mtTyrRSs prior to the evolution of splicing activity, binds group I intron and other RNAs non-specifically via its CTD, but lacks further adaptations needed for group I intron splicing. Our results suggest a scenario of constructive neutral (i.e., pre-adaptive) evolution in which an initial non-specific interaction between the CTD of an ancestral fungal mtTyrRS and a self-splicing group I intron was "fixed" by an intron RNA mutation that resulted in protein-dependent splicing. Once fixed, this interaction could be elaborated by further adaptive mutations in both the catalytic domain and CTD that enabled specific binding of group I introns. Our results highlight a role for non-specific RNA binding in the evolution of RNA-binding proteins.
Source: PLoS Biology
Institution: The University of Texas at Austin
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $5,500
Awards: G102163711, G107546177, G1313983767, G1664757510, G2287611682, G262962599, G3075337988, INVOLVEMENT OF PROTEINS IN SPLICING GROUP I INTRONS, G498139845, G5363686239, G5607048534, G6848031779, G6918803902, Involvement of Proteins in Splicing Group I and II Introns, G8213072523, G9000100676, G969889393, G993149817
OpenAlex ID: W2073345425