Mextli proteins use both canonical bipartite and novel tripartite binding modes to form eIF4E complexes that display differential sensitivity to 4E-BP regulation.
Genes Dev
; 29(17): 1835-49, 2015 Sep 01.
Article
em En
| MEDLINE
| ID: mdl-26294658
ABSTRACT
The eIF4E-binding proteins (4E-BPs) are a diverse class of translation regulators that share a canonical eIF4E-binding motif (4E-BM) with eIF4G. Consequently, they compete with eIF4G for binding to eIF4E, thereby inhibiting translation initiation. Mextli (Mxt) is an unusual 4E-BP that promotes translation by also interacting with eIF3. Here we present the crystal structures of the eIF4E-binding regions of the Drosophila melanogaster (Dm) and Caenorhabditis elegans (Ce) Mxt proteins in complex with eIF4E in the cap-bound and cap-free states. The structures reveal unexpected evolutionary plasticity in the eIF4E-binding mode, with a classical bipartite interface for Ce Mxt and a novel tripartite interface for Dm Mxt. Both interfaces comprise a canonical helix and a noncanonical helix that engage the dorsal and lateral surfaces of eIF4E, respectively. Remarkably, Dm Mxt contains a C-terminal auxiliary helix that lies anti-parallel to the canonical helix on the eIF4E dorsal surface. In contrast to the eIF4G and Ce Mxt complexes, the Dm eIF4E-Mxt complexes are resistant to competition by bipartite 4E-BPs, suggesting that Dm Mxt can bind eIF4E when eIF4G binding is inhibited. Our results uncovered unexpected diversity in the binding modes of 4E-BPs, resulting in eIF4E complexes that display differential sensitivity to 4E-BP regulation.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Modelos Moleculares
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Regulação da Expressão Gênica
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Proteínas de Caenorhabditis elegans
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Proteínas de Drosophila
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Domínios e Motivos de Interação entre Proteínas
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
Genes Dev
Assunto da revista:
BIOLOGIA MOLECULAR
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Alemanha