THE YEAST PROTEIN ARC1P BINDS TO TRANSFER-RNA AND FUNCTIONS AS A COFACTOR FOR THE METHIONYL-TRANSFER-RNA AND GLUTAMYL-TRANSFER-RNA SYNTHETASES

Arc1p was found in a screen for components that interact genetically w ith Los1p, a nuclear pore-associated yeast protein involved in tRNA bi ogenesis. Arc1p is associated with two proteins which were identified as methionyl-tRNA and glutamyl-tRNA synthetase (MetRS and GluRS) by a new mass spectrometry method, ARC1 gene disruption leads to slow growt h and reduced MetRS activity, and synthetically lethal arc1(-) mutants are complemented by the genes for MetRS and GluRS, Recombinant Arc1p binds in vitro to purified monomeric yeast MetRS, but not to an N-term inal truncated form, and strongly increases its apparent affinity for tRNA(Met), Furthermore, Arclp, which is allelic to the quadruplex nucl eic acid binding protein G4p1, exhibits specific binding to tRNA as de termined by gel retardation and UV-cross-linking, Arclp is, therefore, a yeast protein with dual specificity: it associates with tRNA and am inoacyl-tRNA synthetases, This functional interaction may be required for efficient aminoacylation in vivo.