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Originally published as Genetics Published Articles Ahead of Print on September 1, 2006.

Genetics, Vol. 174, 651-663, October 2006, Copyright © 2006
doi:10.1534/genetics.106.059899

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Unique Classes of Mutations in the Saccharomyces cerevisiae G-Protein Translation Elongation Factor 1A Suppress the Requirement for Guanine Nucleotide Exchange

Sedide B. Ozturk*, Melanie R. Vishnu*, Olubunmi Olarewaju*, Lea M. Starita*, Daniel C. Masison{dagger} and Terri Goss Kinzy*,1

* Department of Molecular Genetics, Microbiology and Immunology, UMDNJ Robert Wood Johnson Medical School, Piscataway, New Jersey 08854 and {dagger} Laboratory of Biochemistry and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892

1 Corresponding author: Department of Molecular Genetics, Microbiology and Immunology, UMDNJ Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635.
E-mail: kinzytg{at}umdnj.edu

G-proteins play critical roles in many cellular processes and are regulated by accessory proteins that modulate the nucleotide-bound state. Such proteins, including eukaryotic translation elongation factor 1A (eEF1A), are frequently reactivated by guanine nucleotide exchange factors (GEFs). In the yeast Saccharomyces cerevisiae, only the catalytic subunit of the GEF complex, eEF1B{alpha}, is essential for viability. The requirement for the TEF5 gene encoding eEF1B{alpha} can be suppressed by the presence of excess substrate, eEF1A. These cells, however, have defects in growth and translation. Two independent unbiased screens performed to dissect the cause of these phenotypes yielded dominant suppressors that bypass the requirement for extra eEF1A. Surprisingly, all mutations are in the G-protein eEF1A and cluster in its GTP-binding domain. Five mutants were used to construct novel strains expressing only the eEF1A mutant at normal levels. These strains show no growth defects and little to no decreases in total translation, which raises questions as to the evolutionary expression of GEF complexity and other potential functions of this complex. The location of the mutations on the eEF1A-eEF1B{alpha} structure suggests that their mechanism of suppression may depend on effects on the conserved G-protein elements: the P-loop and NKXD nucleotide-binding element.






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Copyright © 2006 by the Genetics Society of America.