Overexpression of translation elongation factor 1A affects the organization and function of the actin cytoskeleton in yeast

The translation elongation factor I complex (eEF1) plays a central role in protein synthesis, delivering aminoacyl-tRNAs to the elongating ribosome. T he eEF1A subunit, a classic G-protrein also performs roles aside from prote in synthesis. The overexpression of either eEF1A or eEF1B alpha, the cataly tic subunit of the guanine nucleotide exchange factor, in Saccharomyces cer evisiae results in effects on cell growth. Here we demonstrate that overexp ression of either factor does not affect the levels of the other subunit or the rate or accuracy of protein synthesis. Instead, the major effects in v ivo appear to be at the of cell morphology and budding. eEF1A overexpressio n results in dosage-dependent reduced budding and altered actin distributio n and cellular morphology. In addition, the effects of excess eEF1A in acti n mutant strains show synthetic growth defects, establishing a genetic conn ection between tile two proteins. As the ability of eEF1A to bind and bundl e actin is conserved in yeast, these results link the established ability o f eEF1A to bind and bundle actin in vitro with nontranslational roles for t he protein in vivo.