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A novel inhibitor of cap‐dependent translation initiation in yeast: p20 competes with eIF4G for binding to eIF4E
Author(s) -
Altmann Michael,
Schmitz Nicole,
Berset Catherine,
Trachsel Hans
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.5.1114
Subject(s) - eif4g , eif4e , biology , eukaryotic translation , five prime untranslated region , initiation factor , eukaryotic translation initiation factor 4 gamma , poly(a) binding protein , microbiology and biotechnology , translation (biology) , messenger rna , biochemistry , gene
In the yeast Saccharomyces cerevisiae a small protein named p20 is found associated with translation initiation factor eIF4E, the mRNA cap‐binding protein. We demonstrate here that p20 is a repressor of cap‐dependent translation initiation. p20 shows amino acid sequence homology to a region of eIF4G, the large subunit of the cap‐binding protein complex eIF4F, which carries the binding site for eIF4E. Both, eIF4G and p20 bind to eIF4E and compete with each other for binding to eIF4E. The eIF4E–p20 complex can bind to the cap structure and inhibit cap‐dependent but not cap‐independent translation initiation: the translation of a mRNA with the 67 nucleotide Ω sequence of tobacco mosaic virus in its 5′ untranslated region (which was previously shown to render translation cap‐independent) is not inhibited by p20. Whereas the translation of the same mRNA lacking the Ω sequence is strongly inhibited by p20. Disruption of CAF20 , the gene encoding p20, stimulates the growth of yeast cells, overexpression of p20 causes slower growth of yeast cells. These results show that p20 is a regulator of eIF4E activity which represses cap‐dependent initiation of translation by interfering with the interaction of eIF4E with eIF4G, e.g. the formation of the eIF4F–complex.