The Yeast Eukaryotic Translation Initiation Factor 2B Translation Initiation Complex Interacts with the Fatty Acid Synthesis Enzyme YBR159W and Endoplasmic Reticulum Membranes

Abstract

Using affinity purifications coupled with mass spectrometry and yeast two-hybrid assays, we show the Saccharomyces cerevisiae translation initiation factor complex eukaryotic translation initiation factor 2B (eIF2B) and the very-long-chain fatty acid (VLCFA) synthesis keto-reductase enzyme YBR159W physically interact. The data show that the interaction is specifically between YBR159W and eIF2B and not between other members of the translation initiation or VLCFA pathways. A ybr159wΔ null strain has a slow-growth phenotype and a reduced translation rate but a normal GCN4 response to amino acid starvation. Although YBR159W localizes to the endoplasmic reticulum membrane, subcellular fractionation experiments show that a fraction of eIF2B cofractionates with lipid membranes in a YBR159W-independent manner. We show that a ybr159wΔ yeast strain and other strains with null mutations in the VLCFA pathway cause eIF2B to appear as numerous foci throughout the cytoplasm.

ACKNOWLEDGMENTS

C.M.B. was supported by National Institutes of Health (NIH) training grant T32 AI007611, and P.S. and A.J.L. were supported by NIH grant GM64779. The experiments, data analysis, and presentation of fluorescence microscope images were performed in part through the use of the VUMC Cell Imaging Shared Resource, which is supported by NIH grants CA68485, DK20593, DK58404, HD15052, and DK59637.

We thank Tom Dever, Alan Hinnebusch, Howard Riezman, and Jonathan Warner for reagents and yeast strains.