Binding of eukaryotic initiation factor 3 to ribosomal 40S subunits and its role in ribosomal dissociation and anti-association

Kolupaeva, Victoria G.; Unbehaun, Anett; Lomakin, Ivan B.; Hellen, Christopher U.T.; Pestova, Tatyana V.

doi:10.1261/rna.7215305

Cited by 115 publications

(147 citation statements)

References 76 publications

(116 reference statements)

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“…eIF3 is a canonical initiation factor that interacts with the 40S subunit (8,9). Enrichment of DHX29 in 40S fractions in vivo is in agreement with the in vitro data (7) and consistent with the suggested function of DHX29 at the translation initiation stage.…”

Section: Dhx29 Is a Ubiquitously Expressed Cytoplasmic Protein That Asupporting

confidence: 88%

The helicase protein DHX29 promotes translation initiation, cell proliferation, and tumorigenesis

Parsyan

Shahbazian²,

Martineau³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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104

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Translational control plays an important role in cell growth and tumorigenesis. Cap-dependent translation initiation of mammalian mRNAs with structured 5 UTRs requires the DExH-box protein, DHX29, in vitro. Here we show that DHX29 is important for translation in vivo. Down-regulation of DHX29 leads to impaired translation, resulting in disassembly of polysomes and accumulation of mRNA-free 80S monomers. DHX29 depletion also impedes cancer cell growth in culture and in xenografts. Thus, DHX29 is a bona fide translation initiation factor that potentially can be exploited as a target to inhibit cancer cell growth.I nitiation is a tightly regulated rate-limiting step in the translation of eukaryotic mRNAs. Ribosome recruitment to the mRNA commences with binding of translation initiation factor 4F (eIF4F) to the 7-methyl guanosine cap structure, which is present at the 5Ј end of all nuclear-encoded eukaryotic mRNAs (1). eIF4F (comprising the cap-binding protein eIF4E, the DEAD-box RNA helicase eIF4A and eIF4G, a scaffold for binding eIF4E and eIF4A) binds to the cap, unwinds (with the aid of eIF4A) the cap-proximal region of the mRNA, and, through interaction with the ribosome-bound eIF3, recruits the 40S ribosomal subunit to the mRNA (2-4). The 40S subunit then scans the 5Ј UTR in a 5Ј to 3Ј direction until it encounters an initiation codon. A subsequent joining of the 60S ribosomal subunit and release of eIFs result in formation of an elongationcompetent 80S ribosome.Secondary structures in 5ЈUTRs of mRNAs are thought to become unwound to allow ribosomal complexes to move along the mRNA in search of the initiation codon. Thus, in addition to its role in the initial attachment of ribosomal complexes to mRNA, eIF4A is believed to assist ribosomal complexes during scanning (5). Recent observations suggest that the process of eukaryotic initiation requires additional members of the DEAD/DExH-box protein family; for instance, a DEAD-box protein, yeast Ded1, and its mammalian homologue, DDX3, are biochemically and genetically implicated in translation initiation on long structured 5ЈUTRs (6), and another DExH-box protein, DHX29, strongly stimulates cap-dependent initiation on mRNAs with structured 5ЈUTRs in vitro (7). Here we studied the importance of DHX29 for translation in vivo and characterized it as a novel factor required for cell proliferation. Results DHX29 Is a Ubiquitously Expressed Cytoplasmic Protein That Associ-ates with the 40S Ribosomal Subunit. DHX29 has been found to interact with the 40S ribosomal subunit in vitro and to associate with 40S ribosomal complexes in a rabbit reticulocyte lysate (7). To determine how general these findings are, we examined the distribution of DHX29 in polysome preparations from HeLa cells using 2 commercial DHX29 antibodies (Fig. 1A). The specificity of these antibodies to human DHX29 was confirmed by immunoblotting against the purified native protein [supporting information (SI) Fig. S1] and recombinant DHX29, as well as by the loss of immunoreactivity following DHX29 RNAi ...

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Section: Dhx29 Is a Ubiquitously Expressed Cytoplasmic Protein That Asupporting

confidence: 88%

The helicase protein DHX29 promotes translation initiation, cell proliferation, and tumorigenesis

Parsyan

Shahbazian²,

Martineau³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

104

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“…eIF3 also impedes 40S-60S subunit association. 42,43 Studies in a reconstituted yeast system have shown that eIF3 (and eIF5) enhances TC binding to the 43S initiation complex. 25,[44][45][46] In addition, genetic and biochemical data have shown that eIF3 can exist as part of a MFC along with eIF1, eIF5 and TC prior to 43S/48S complex formation.…”

Section: E999576-4mentioning

confidence: 99%

Eukaryote-specific extensions in ribosomal proteins of the small subunit: Structure and function

Ghosh

Komar

2015

Translation

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Keywords: conserved ribosomal proteins, eukaryotic/yeast ribosome, eukaryote-specific extensions, eukaryotic translation initiation factors, protein synthesis, small ribosomal subunitHigh-resolution structures of yeast ribosomes have improved our understanding of the architecture and organization of eukaryotic rRNA and proteins, as well as eukaryote-specific extensions present in some conserved ribosomal proteins. Despite this progress, assignment of specific functions to individual proteins and/or eukaryotespecific protein extensions remains challenging. It has been suggested that eukaryote-specific extensions of conserved proteins from the small ribosomal subunit may facilitate eukaryote-specific reactions in the initiation phase of protein synthesis. This review summarizes emerging data describing the structural and functional significance of eukaryotespecific extensions of conserved small ribosomal subunit proteins, particularly their possible roles in recruitment and spatial organization of eukaryote-specific initiation factors.

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“…Although eIF3j is a component of a binary eIF3⅐40 S complex, it is no longer associated with eIF3 and the 40 S subunit in the presence of mRNA as well as in 48 S complexes (4,28). In such ribosomal particles lacking eIF3j, interactions of eIF3a, eIF3b, and eIF3d with mRNA (28) might then instead support the stable association of eIF3 with the 40 S subunit and thereby replace the requirement of eIF3j for stable eIF3/40 S binding.…”

Section: Eif3b-rrm Resembles Noncanonical Rrms Of the U2afmentioning

confidence: 99%

“…The initiation phase of protein synthesis requires at least 12 eukaryotic initiation factors (eIFs) 4 to assemble 80 S ribosomes onto mRNA with the anticodon of tRNA i Met base-paired to the authentic AUG start codon (for a review, see Ref. 1).…”

mentioning

confidence: 99%

“…3). In addition, eIF3 is involved in the dissociation of 80 S ribosomes from mRNA after termination of translation and serves as an anti-association factor preventing 60 S subunit binding to 40 S subunits prior to the subsequent 48 S initiation complex formation (4,5). The recent cryoelectron microscopy structure of free human eIF3 revealed an overall five-lobed architecture particle (6).…”

mentioning

confidence: 99%

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Structure of eIF3b RNA Recognition Motif and Its Interaction with eIF3j

ElAntak¹,

Tzakos²,

Locker³

et al. 2007

Journal of Biological Chemistry

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Mammalian eIF3 is a 700-kDa multiprotein complex essential for initiation of protein synthesis in eukaryotic cells. It consists of 13 subunits (eIF3a to -m), among which eIF3b serves as a major scaffolding protein. Here we report the solution structure of the N-terminal RNA recognition motif of human eIF3b (eIF3b-RRM) determined by NMR spectroscopy. The structure reveals a noncanonical RRM with a negatively charged surface in the ␤-sheet area contradictory with potential RNA binding activity. Instead, eIF3j, which is required for stable 40 S ribosome binding of the eIF3 complex, specifically binds to the rear ␣-helices of the eIF3b-RRM, opposite to its ␤-sheet surface. Moreover, we identify that an N-terminal 69-amino acid peptide of eIF3j is sufficient for binding to eIF3b-RRM and that this interaction is essential for eIF3b-RRM recruitment to the 40 S ribosomal subunit. Our results provide the first structure of an important subdomain of a core eIF3 subunit and detailed insights into protein-protein interactions between two eIF3 subunits required for stable eIF3 recruitment to the 40 S subunit.

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Binding of eukaryotic initiation factor 3 to ribosomal 40S subunits and its role in ribosomal dissociation and anti-association

Cited by 115 publications

References 76 publications

The helicase protein DHX29 promotes translation initiation, cell proliferation, and tumorigenesis

The helicase protein DHX29 promotes translation initiation, cell proliferation, and tumorigenesis

Eukaryote-specific extensions in ribosomal proteins of the small subunit: Structure and function

Structure of eIF3b RNA Recognition Motif and Its Interaction with eIF3j

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