Use of a synthetic lethal screen to identify genes related to

Abstract

The putative eukaryotic translation initiation factor 5A (eIF5A) is an essential protein for cell viability and the only cellular pro- tein known to contain the unusual amino acid residue hypusine. eIF5A has been implicated in translation initiation, cell proliferation, nucleocyto- plasmic transport, mRNA decay, and actin polarization, but the precise biological function of this protein is not clear. However, eIF5A was re- cently shown to be directly involved with the translational machinery. A screen for synthetic lethal mutations was carried out with one of the temperature-sensitive alleles of TIF51A (tif51A-3) to identify factors that functionally interact with eIF5A and revealed the essential gene YPT1. This gene encodes a small GTPase, a member of the rab family involved with secretion, acting in the vesicular trafficking between endoplasmatic reticulum and the Golgi. Thus, the synthetic lethality be- tween TIF51A and YPT1 may reveal the connection between transla- tion and the polarized distribution of membrane components, suggesting that these proteins work together in the cell to guarantee proper protein synthesis and secretion necessary for correct bud formation during G1/ S transition. Future studies will investigate the functional interaction be- tween eIF5A and Ypt1 in order to clarify this involvement of eIF5A with vesicular trafficking.