Talk abstracts

Talk on Friday 03:10-03:30pm submitted by Partho Sarothi Ray

The Origin and Evolution of an mRNA-binding Domain in Glutamyl-prolyl tRNA Synthetase

Partho Sarothi Ray (Dept. of Cell Biology, Lerner Research Institute, Cleveland Clinic), Paul L. Fox (Dept. of Cell Biology, Lerner Research Institute, Cleveland Clinic)

Abstract:
The catalytic domains of the aminoacyl tRNA synthetases (ARS) are of ancient origin and conserved across bacteria, archaea and eukaryotes. However, several ARSs have appended non-enzymatic domains, which may mediate non-canonical activities. The WHEP-TRS domain is a non-enzymatic domain found in five eukaryotic ARSs. In glutamyl-prolyl tRNA synthetase (EPRS) of animals, this domain exists in multiple repeats of variable number in the linker region between the two enzymatic domains. Results from our laboratory suggest that the WHEP-TRS domain of human EPRS is required for transcript-selective translational silencing and has both RNA-binding and protein-binding abilities. Investigating the origin and evolution of the WHEP domains can provide insights into the origin of EPRS and the evolution of its non-canonical activity. Previous analysis based on the presence of unlinked ERS and PRS in C. elegans had suggested that EPRS originated by a gene fusion event early in coelomate evolution, giving rise to EPRS with six WHEP repeats; subsequent deletions in vertebrates resulted in EPRS with three WHEP domains. We have cloned the EPRS WHEP domain from basal eukaryotic taxa (choanoflagellates and cnidarians) and performed protein phylogeny analysis using these sequences in combination with a large dataset of available WHEP sequences. Our results show for the first time that the bifunctional EPRS with WHEP domains originated by a gene fusion event before the origin of animals. Cloning and phylogenetic analysis of early chordate WHEP domains (cephalochordates and urochordates) suggest that the domain evolved by repeated duplications with divergence in multiple metazoan lineages. RNA-protein interaction studies using surface plasmon resonance suggest that the early WHEP domains had both mRNA and tRNA-binding functions. These data trace the origin of the only bifunctional ARS in eukaryotes. Independent duplication in multiple species and long-term persistence suggest that the WHEP repeats contribute to a unique mRNA-binding function of EPRS.

Keywords: tRNA synthetase, mRNA-binding domain, evolution