PUBLICATION
Distinct features of cap-binding by eIF4E1b proteins
- Authors
- Kubacka, D., Miguel, R.N., Minshall, N., Darzynkiewicz, E., Standart, N., Zuberek, J.
- ID
- ZDB-PUB-141203-7
- Date
- 2015
- Source
- Journal of molecular biology 427(2): 387-405 (Journal)
- Registered Authors
- Keywords
- Xenopus laevis, binding affinity, eIF4E1b, eukaryotic initiation factor, translational repression
- MeSH Terms
-
- Models, Molecular
- Protein Binding*
- Xenopus laevis
- Carrier Proteins/genetics
- Carrier Proteins/metabolism*
- Humans
- Sepharose/analogs & derivatives
- Sepharose/chemistry
- Sepharose/genetics
- Eukaryotic Initiation Factor-4E/genetics
- Eukaryotic Initiation Factor-4E/metabolism*
- Binding Sites/genetics
- Gene Expression Regulation
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Protein Conformation
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Animals
- Guanosine Triphosphate/analogs & derivatives
- Guanosine Triphosphate/chemistry
- Guanosine Triphosphate/genetics
- Sequence Alignment
- Cloning, Molecular
- PubMed
- 25463438 Full text @ J. Mol. Biol.
Citation
Kubacka, D., Miguel, R.N., Minshall, N., Darzynkiewicz, E., Standart, N., Zuberek, J. (2015) Distinct features of cap-binding by eIF4E1b proteins. Journal of molecular biology. 427(2):387-405.
Abstract
eIF4E1b, closely related to the canonical translation initiation factor 4E (eIF4E1a), cap-binding protein, is highly expressed in mouse, Xenopus and zebrafish oocytes. We have previously characterised eIF4E1b as a component of the CPEB mRNP translation repressor complex along with the eIF4E-binding protein 4E-Transporter, the Xp54/DDX6 RNA helicase and additional RNA-binding proteins. eIF4E1b exhibited only very weak interactions with m(7)GTP-Sepharose and rather than binding eIF4G, interacted with 4E-T. Here we undertook a detailed examination of both Xenopus and human eIF4E1b interactions with cap analogues using fluorescence titration and homology modeling. The predicted structure of eIF4E1b maintains the α+β fold characteristic of eIF4E proteins and its cap-binding pocket is similarly arranged by critical amino acids: Trp56, Trp102, Glu103, Trp166, Arg112, Arg157, Lys162 and residues of the C-terminal loop. However, we demonstrate that eIF4E1b is three-fold less well able to bind the cap than eIF4E1a, both proteins being highly stimulated by methylation at N(7) of guanine. Moreover, eIF4E1b proteins are distinguishable from eIF4E1a by a set of conserved amino acid substitutions, several of which are located near to cap-binding residues. Indeed, eIF4E1b possesses several distinct features, namely enhancement of cap-binding by a benzyl group at N(7) position of guanine, a reduced response to increasing length of the phosphate chain and increased binding to a cap separated by a linker from Sepharose, suggesting differences in the arrangement of the protein's core. In agreement, mutagenesis of the amino acids differentiating eIF4E1b from eIF4E1a reduces cap-binding by eIF4E1a two-fold, demonstrating their role in modulating cap-binding.
Genes / Markers
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping