The plant translational apparatus

Browning, Karen S.

doi:10.1007/bf00039380

Cited by 206 publications

(205 citation statements)

References 354 publications

(369 reference statements)

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“…The initiation factor eIF4G has been isolated and cloned from many different species including the yeasts S. cerevisiae and S. pombe (Goyer et al, 1993), Drosophila (Zapata et al, 1994), wheat (Browning, 1996) and human (Gradi et al, 1998a;Yan et al, 1992). There are two isoforms of eIF4G in wheat (eIF4G and iso-eIF4G), S. cerevisiae (TIF4631 and TIF4632) and human (eIF4GI and eIF4GII; eIF4GI being the prototype member of the family) which exhibit moderate sequence conservation (46% identity in human, 53% in yeast) but share similar overall biochemical activities, although some differences were observed between the yeast and wheat isoforms (Gallie and Browning, 2001;Tarun et al, 1997).…”

Section: The Eif4g Familymentioning

confidence: 99%

Conducting the initiation of protein synthesis: the role of eIF4G

Prévot

Darlix

Ohlmann

2003

Biology of the Cell

200

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The eukaryotic initiation factor eIF4G is a large modular protein which serves as a docking site for initiation factors and proteins involved in RNA translation. Together with eIF4E and eIF4A, eIF4G constitutes the eIF4F complex which is a key component in promoting ribosome binding to the mRNA. Thus, the central role of eIF4G in initiation makes it a valid target for events aimed at modulating translation. Such events occur during viral infection by picornaviruses and lentiviruses and result in the hijack of the translational machinery through cleavage of eIF4G. Proteolysis of eIF4G is also mediated by caspases during the onset of apoptosis causing inhibition of protein synthesis. We will review the role of eIF4G and protein partners as well as the cellular and viral events that modulate eIF4G activity in the initiation of translation.

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Section: The Eif4g Familymentioning

confidence: 99%

Conducting the initiation of protein synthesis: the role of eIF4G

Prévot

Darlix

Ohlmann

2003

Biology of the Cell

200

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“…A key regulatory point for translation initiation is the binding of the 43S preinitiation complex (40S ribosomal subunit charged with the initiator methionine t-RNA) to the 5' end of the mRNA, catalyzed by an initiation factor complex, eIF4F (reviewed in Browning, 1996;Pestova and Hellen, 2001;Gallie, 2002;Gingras et al, 1999). eIF4F is a ternary complex consisting of eIF4E, the capbinding subunit, eIF4A, a DEAD-box RNA helicase, and eIF4G, a bridging polypeptide that interacts with eIF4A, eIF4E and the 40S ribosomal subunit via contacts with the eIF3 multi-subunit complex.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to eIF4F, flowering plants contain a second cap-binding complex called eIFiso4F, which is composed of different eIF4E and eIF4G subunits (reviewed in Browning 1996). In wheat germ, eIF4F consists of a 220 KDa eIF4G polypeptide and a 26 KDa cap-binding protein called eIF4E.…”

Section: Introductionmentioning

confidence: 99%

“…The published eIF4E and eIFiso4E sequences, from monocot and dicot plants species, share 45-50% identity at the amino acid level, whereas Arabidopsis and wheat eIFiso4G and eIF4G are only 30-40% identical. Wheat eIF4F and eIFiso4F have similar biochemical properties and are both able to support protein synthesis within a fractionated wheat germ translation system (Browning, 1996). When present at rate-limiting amounts, eIF4F and eIFiso4F differentially support the in vitro translation of some mRNAs, suggesting that the two cap-binding complexes have evolved to regulate plant translation by mRNA selection (Gallie, 2001;Gallie and Browning, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Translation initiation factors eIF4E and eIFiso4E are required for polysome formation and regulate plant growth in tobacco

et al. 2005

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eIF4E and eIFiso4E T AbstractEukaryotic initiation factor eIF4E plays a pivotal role in translation initiation. As a component of the ternary eIF4F complex, eIF4E interacts with the mRNA cap structure to facilitate recruitment of the 40S ribosomal subunit onto mRNA. Plants contain two distinct cap-binding proteins, eIF4E and eIFiso4E, that assemble into different eIF4F complexes. To study the functional roles of eIF4E and eIFiso4E in tobacco, we isolated two corresponding cDNAs, NteIF4E1 and NteIFiso4E1, and used these to deplete cap-binding protein levels in planta by antisense downregulation. Antibodies raised against recombinant NteIF4E1 detected three distinct cap-binding proteins in tobacco leaf extracts; NteIF4E and two isoforms of NteIFiso4E. The three cap-binding proteins were immuno-detected in all tissues analysed and were coordinately regulated, with peak expression in anthers and pollen. Transgenic tobacco plants showing significant depletion of either NteIF4E or the twoNteIFiso4E isoforms displayed normal vegetative development and were fully fertile.Interestingly, NteIFiso4E depletion resulted in a compensatory increase in NteIF4E levels, whereas the down-regulation of NteIF4E did not trigger a reciprocal increase in NteIFiso4E levels. The antisense depletion of both NteIF4E and NteIFiso4E resulted in plants with a semi-dwarf phenotype and an overall reduction in polyribosome loading, demonstrating that both eIF4E and eIFiso4E support translation initiation in planta, which suggests their potential role in the regulation of plant growth.

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“…eIF4A may also be present in the eIF4E⅐eIF4G complex depending upon the method of purification (7,8). Higher plants possess a unique second form of eIF4F designated eIF(iso)4F (9). eIF(iso)4F contains distinct forms of the cap-binding protein (eIF(iso)4E) and the larger subunit (eIF(iso)4G) (10).…”

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confidence: 99%

Identification and Characterization of a Novel Cap-binding Protein from Arabidopsis thaliana

Ruud¹,

Kuhlow²,

Goss³

et al. 1998

Journal of Biological Chemistry

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Cap-binding proteins specifically bind to the 7-methyl guanosine (m 7 G) functional group at the 5 end of eukaryotic mRNAs. A novel Arabidopsis thaliana protein has been identified that has sequence similarity to capbinding proteins but is clearly a different form of the protein. The most obvious primary sequence difference is the substitution of two of the eight conserved tryptophan residues with other aromatic amino acids in the novel protein. Analogous forms of this novel protein appear to be present in other higher eukaryotes but not in yeast. Analysis of the native and recombinant forms of the novel protein by retention on m 7 GTP-Sepharose indicate that it is a functional cap-binding protein. Measurements of the dissociation constant for this protein indicate that it binds m 7 GTP 5-20-fold tighter than eukaryotic initiation factor (eIF)(iso)4E. The novel protein also supports the initiation of translation of capped mRNA in vitro. Biochemical analysis and yeast two-hybrid data indicate that it interacts with eIF(iso)4G to form a complex. Based on these observations, this protein appears to be able to function as a cap-binding protein and is given the designation of novel cap-binding protein (nCBP).Cap-binding proteins (eIF4E) 1 specifically recognize and bind the m 7 G functional group found at the 5Ј end of most eukaryotic cellular mRNAs (for recent reviews, see Refs. 1 and 2). The binding of eIF4E is thought to be the first step in the assembly of several initiation factors on the mRNA prior to the binding of the 40 S ribosome (1-3). One of the structural features of all eIF4E proteins is the presence of eight tryptophan residues in the same relative positions. Recently, the cocrystal structures of the mouse eIF4E (4) and yeast eIF4E (5) with m 7 GDP were solved. Tryptophan residues 3, 5, and 8 were found to be involved in binding the m 7 G functional group (4,5). eIF4E is usually associated with a larger subunit (eIF4G) in a complex named eIF4F (1, 6). eIF4A may also be present in the eIF4E⅐eIF4G complex depending upon the method of purification (7,8). Higher plants possess a unique second form of eIF4F designated eIF(iso)4F (9). eIF(iso)4F contains distinct forms of the cap-binding protein (eIF(iso)4E) and the larger subunit (eIF(iso)4G) (10). The two isoenzyme forms of plant eIF4F have the same activities in vitro (9); however, the eIF(iso)4E prefers hypermethylated caps and mRNAs with less secondary structure (11,12). Recently, a second form of mammalian eIF4G was reported (13). However, this form of eIF4G was not reported to have a distinct form of eIF4E associated with it and does not appear to be the functional equivalent of eIF(iso)4G.The mammalian eIF4E is known to be phosphorylated at Ser-209, and the phosphorylation state appears to correlate with activity of the protein (reviewed in Refs. 14 and 15). Certain stimuli, including insulin and several growth factors, induce phosphorylation of eIF4E (14). Overexpression of the mammalian eIF4E results in cell transformation, suggesting that eIF4E le...

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The plant translational apparatus

Cited by 206 publications

References 354 publications

Conducting the initiation of protein synthesis: the role of eIF4G

Conducting the initiation of protein synthesis: the role of eIF4G

Translation initiation factors eIF4E and eIFiso4E are required for polysome formation and regulate plant growth in tobacco

Identification and Characterization of a Novel Cap-binding Protein from Arabidopsis thaliana

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