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The binding of eukaryotic initiation factor 5A to the translation active 80S ribosomes in vivo is hypusine‐ and RNA‐dependent
Author(s) -
Chen Kuang Yu,
Jao David Lien
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a109-b
Subject(s) - ribosome , initiation factor , in vivo , eukaryotic initiation factor , translation (biology) , eukaryotic translation , eukaryotic ribosome , microbiology and biotechnology , chemistry , eif4e , eif2 , rna , biology , biochemistry , messenger rna , genetics , gene
Eukariyotic initiation factor 5A (eIF5A) is the only protein in nature that contains the unusual amino acid hypusine. Genes encoding eIF5A or deoxyhypusine synthase are essential for cell survival and proliferation. To determine the function of eIF5A, we have employed the tandem affinity purification (TAP) and mass spectrometry to search for and identify the binding partners of eIF5A. The TAP‐tag was fused in‐frame to chromosomal TIF51A gene and eIF5A‐TAP fusion protein expressed at its natural level was used as the bait to fish out its binding partners. As a comparison, we have performed similar TAP procedure with eIF4E. We have identified the intact 80S ribosome as the major interacting partner of eIF5A. In addition, eEF1A, zuotin, ssb2p, YPL207W and Clu1/TIF31 are present in the binding complex. This unique eIF5A‐ribosome binding absolutely requires the presence of hypusine residue on eIF5A. Moreover, the interaction is very sensitive to RNase treatment. In contrast, eIF4E binds to a set of proteins including eIF4GI and II, p20, p210, p24, sse1p, and ssb1p. The binding of the eIF5A to the 80S ribosomes is greatly diminished when cells are in the stationary phase of growth. Our data suggest that eIF5A is not involved in the initiation steps of translation. Instead, the essential function of eIF5A is mostly likely mediated through its interaction with the actively translating ribosomes.