scholarly journals The translation initiation factor eIF-4B contains an RNA-binding region that is distinct and independent from its ribonucleoprotein consensus sequence.

1994 ◽  
Vol 14 (4) ◽  
pp. 2307-2316 ◽  
Author(s):  
N Méthot ◽  
A Pause ◽  
J W Hershey ◽  
N Sonenberg
Keyword(s):  
Translation Initiation ◽  
Rna Binding ◽  
Consensus Sequence ◽  
Point Mutations ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Rna Recognition Motif ◽  
Helicase Activity ◽  
Binding Region ◽  
Stimulation Of

eIF-4B is a eukaryotic translation initiation factor that is required for the binding of ribosomes to mRNAs and the stimulation of the helicase activity of eIF-4A. It is an RNA-binding protein that contains a ribonucleoprotein consensus sequence (RNP-CS)/RNA recognition motif (RRM). We examined the effects of deletions and point mutations on the ability of eIF-4B to bind a random RNA, to cooperate with eIF-4A in RNA binding, and to enhance the helicase activity of eIF-4A. We report here that the RNP-CS/RRM alone is not sufficient for eIF-4B binding to RNA and that an RNA-binding region, located between amino acids 367 and 423, is the major contributor to RNA binding. Deletions which remove this region abolish the ability of eIF-4B to cooperate with eIF-4A in RNA binding and the ability to stimulate the helicase activity of eIF-4A. Point mutations in the RNP-CS/RRM had no effect on the ability of eIF-4B to cooperate with eIF-4A in RNA binding but significantly reduced the stimulation of eIF-4A helicase activity. Our results indicate that the carboxy-terminal RNA-binding region of eIF-4B is essential for eIF-4B function and is distinct from the RNP-CS/RRM.

The translation initiation factor eIF-4B contains an RNA-binding region that is distinct and independent from its ribonucleoprotein consensus sequence

1994 ◽  
Vol 14 (4) ◽  
pp. 2307-2316
Author(s):  
N Méthot ◽  
A Pause ◽  
J W Hershey ◽  
N Sonenberg
Keyword(s):  
Translation Initiation ◽  
Rna Binding ◽  
Consensus Sequence ◽  
Point Mutations ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Rna Recognition Motif ◽  
Helicase Activity ◽  
Binding Region ◽  
Stimulation Of

eIF-4B is a eukaryotic translation initiation factor that is required for the binding of ribosomes to mRNAs and the stimulation of the helicase activity of eIF-4A. It is an RNA-binding protein that contains a ribonucleoprotein consensus sequence (RNP-CS)/RNA recognition motif (RRM). We examined the effects of deletions and point mutations on the ability of eIF-4B to bind a random RNA, to cooperate with eIF-4A in RNA binding, and to enhance the helicase activity of eIF-4A. We report here that the RNP-CS/RRM alone is not sufficient for eIF-4B binding to RNA and that an RNA-binding region, located between amino acids 367 and 423, is the major contributor to RNA binding. Deletions which remove this region abolish the ability of eIF-4B to cooperate with eIF-4A in RNA binding and the ability to stimulate the helicase activity of eIF-4A. Point mutations in the RNP-CS/RRM had no effect on the ability of eIF-4B to cooperate with eIF-4A in RNA binding but significantly reduced the stimulation of eIF-4A helicase activity. Our results indicate that the carboxy-terminal RNA-binding region of eIF-4B is essential for eIF-4B function and is distinct from the RNP-CS/RRM.

scholarly journals Requirement of RNA Binding of Mammalian Eukaryotic Translation Initiation Factor 4GI (eIF4GI) for Efficient Interaction of eIF4E with the mRNA Cap

2008 ◽  
Vol 29 (6) ◽  
pp. 1661-1669 ◽  
Author(s):  
Akiko Yanagiya ◽  
Yuri V. Svitkin ◽  
Shoichiro Shibata ◽  
Satoshi Mikami ◽  
Hiroaki Imataka ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Rna Binding ◽  
Binding Activity ◽  
Translation Initiation Factor ◽  
Scaffolding Protein ◽  
Initiation Factor ◽  
Rna Recognition Motif ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation

ABSTRACT Eukaryotic mRNAs possess a 5′-terminal cap structure (cap), m7GpppN, which facilitates ribosome binding. The cap is bound by eukaryotic translation initiation factor 4F (eIF4F), which is composed of eIF4E, eIF4G, and eIF4A. eIF4E is the cap-binding subunit, eIF4A is an RNA helicase, and eIF4G is a scaffolding protein that bridges between the mRNA and ribosome. eIF4G contains an RNA-binding domain, which was suggested to stimulate eIF4E interaction with the cap in mammals. In Saccharomyces cerevisiae, however, such an effect was not observed. Here, we used recombinant proteins to reconstitute the cap binding of the mammalian eIF4E-eIF4GI complex to investigate the importance of the RNA-binding region of eIF4GI for cap interaction with eIF4E. We demonstrate that chemical cross-linking of eIF4E to the cap structure is dramatically enhanced by eIF4GI fragments possessing RNA-binding activity. Furthermore, the fusion of RNA recognition motif 1 (RRM1) of the La autoantigen to the N terminus of eIF4GI confers enhanced association between the cap structure and eIF4E. These results demonstrate that eIF4GI serves to anchor eIF4E to the mRNA and enhance its interaction with the cap structure.

scholarly journals Binding of eukaryotic translation initiation factor 4E (eIF4E) to eIF4G represses translation of uncapped mRNA.

1997 ◽  
Vol 17 (12) ◽  
pp. 6876-6886 ◽  
Author(s):  
S Z Tarun ◽  
A B Sachs
Keyword(s):  
Translation Initiation ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Stimulation Of

mRNA translation in crude extracts from the yeast Saccharomyces cerevisiae is stimulated by the cap structure and the poly(A) tail through the binding of the cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) and the poly(A) tail-binding protein Pab1p. These proteins also bind to the translation initiation factor eIF4G and thereby link the mRNA to the general translational apparatus. In contrast, uncapped, poly(A)-deficient mRNA is translated poorly in yeast extracts, in part because of the absence of eIF4E and Pab1p binding sites on the mRNA. Here, we report that uncapped-mRNA translation is also repressed in yeast extracts due to the binding of eIF4E to eIF4G. Specifically, we find that mutations which weaken the eIF4E binding site on the yeast eIF4G proteins Tif4631p and Tif4632p lead to temperature-sensitive growth in vivo and the stimulation of uncapped-mRNA translation in vitro. A mutation in eIF4E which disturbs its ability to interact with eIF4G also leads to a stimulation of uncapped-mRNA translation in vitro. Finally, overexpression of eIF4E in vivo or the addition of excess eIF4E in vitro reverses these effects of the mutations. These data support the hypothesis that the eIF4G protein can efficiently stimulate translation of exogenous uncapped mRNA in extracts but is prevented from doing so as a result of its association with eIF4E. They also suggest that some mRNAs may be translationally regulated in vivo in response to the amount of free eIF4G in the cell.

scholarly journals An eIF2α-binding motif in protein phosphatase 1 subunit GADD34 and its viral orthologs is required to promote dephosphorylation of eIF2α

2015 ◽  
Vol 112 (27) ◽  
pp. E3466-E3475 ◽  
Author(s):  
Margarito Rojas ◽  
Gabriel Vasconcelos ◽  
Thomas E. Dever
Keyword(s):  
Protein Phosphatase ◽  
African Swine Fever Virus ◽  
Consensus Sequence ◽  
Point Mutations ◽  
Translation Initiation Factor ◽  
Protein Phosphatase 1 ◽  
Initiation Factor ◽  
Protective Mechanism ◽  
Binding Motif ◽  
Α Subunit

Transient protein synthesis inhibition, mediated by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α), is an important protective mechanism cells use during stress conditions. Following relief of the stress, the growth arrest and DNA damage-inducible protein GADD34 associates with the broadly acting serine/threonine protein phosphatase 1 (PP1) to dephosphorylate eIF2α. Whereas the PP1-binding motif on GADD34 has been defined, it remains to be determined how GADD34 directs PP1 to specifically dephosphorylate eIF2α. In this report, we map a novel eIF2α-binding motif to the C terminus of GADD34 in a region distinct from where PP1 binds to GADD34. This motif is characterized by the consensus sequence Rx[Gnl]x1–2Wxxx[Arlv]x[Dn][Rg]xRFxx[Rlvk][Ivc], where capital letters are preferred and x is any residue. Point mutations altering the eIF2α-binding motif impair the ability of GADD34 to interact with eIF2α, promote eIF2α dephosphorylation, and suppress PKR toxicity in yeast. Interestingly, this eIF2α-docking motif is conserved among viral orthologs of GADD34, and is necessary for the proteins produced by African swine fever virus, Canarypox virus, and Herpes simplex virus to promote eIF2α dephosphorylation. Taken together, these data indicate that GADD34 and its viral orthologs direct specific dephosphorylation of eIF2α by interacting with both PP1 and eIF2α through independent binding motifs.

scholarly journals The C-Terminal Region of Eukaryotic Translation Initiation Factor 3a (eIF3a) Promotes mRNA Recruitment, Scanning, and, Together with eIF3j and the eIF3b RNA Recognition Motif, Selection of AUG Start Codons

2010 ◽  
Vol 30 (18) ◽  
pp. 4415-4434 ◽  
Author(s):  
Wen-Ling Chiu ◽  
Susan Wagner ◽  
Anna Herrmannová ◽  
Laxminarayana Burela ◽  
Fan Zhang ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Rna Recognition Motif ◽  
Rna Recognition ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Recognition Motif ◽  
Terminal Domain ◽  
Eukaryotic Translation Initiation

ABSTRACT The C-terminal domain (CTD) of the a/Tif32 subunit of budding yeast eukaryotic translation initiation factor 3 (eIF3) interacts with eIF3 subunits j/Hcr1 and b/Prt1 and can bind helices 16 to 18 of 18S rRNA, suggesting proximity to the mRNA entry channel of the 40S subunit. We have identified substitutions in the conserved Lys-Glu-Arg-Arg (KERR) motif and in residues of the nearby box6 element of the a/Tif32 CTD that impair mRNA recruitment by 43S preinitiation complexes (PICs) and confer phenotypes indicating defects in scanning and start codon recognition. The normally dispensable CTD of j/Hcr1 is required for its binding to a/Tif32 and to mitigate the growth defects of these a/Tif32 mutants, indicating physical and functional interactions between these two domains. The a/Tif32 CTD and the j/Hcr1 N-terminal domain (NTD) also interact with the RNA recognition motif (RRM) in b/Prt1, and mutations in both subunits that disrupt their interactions with the RRM increase leaky scanning of an AUG codon. These results, and our demonstration that the extreme CTD of a/Tif32 binds to Rps2 and Rps3, lead us to propose that the a/Tif32 CTD directly stabilizes 43S subunit-mRNA interaction and that the b/Prt1-RRM-j/Hcr1-a/Tif32-CTD module binds near the mRNA entry channel and regulates the transition between scanning-conducive and initiation-competent conformations of the PIC.

scholarly journals Cancer-associated mRNAs regulated by the Helix-Loop-Helix motif of human EIF3A

2018 ◽  
Author(s):  
Marina Volegova ◽  
Jamie H.D. Cate
Keyword(s):  
Translation Initiation ◽  
Rna Binding ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Binding Motif ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Helix Loop Helix ◽  
Small Set

AbstractImproper regulation of translation initiation, a vital check-point of protein synthesis in the cell, has been linked to a number of cancers. Overexpression of protein subunits of eukaryotic translation initiation factor 3 (eIF3) has been associated with increased translation of mRNAs involved in cell proliferation. In addition to playing a major role in general translation initiation by serving as a scaffold for the assembly of translation initiation complexes, eIF3 regulates translation of specific cellular mRNAs and viral RNAs. Mutations in the N-terminal Helix-Loop-Helix (HLH) RNA-binding motif of the EIF3A subunit in eIF3 interfere with Hepatitis C Virus Internal Ribosome Entry Site (IRES) mediated translation initiationin vitro. Here we show that the EIF3A HLH motif controls translation of a small set of cellular transcripts enriched in oncogenic mRNAs, includingMYC. We also demonstrate that the HLH motif of EIF3A acts specifically on the 5’-UTR ofMYCmRNA and modulates the function of EIF4A1 on select transcripts during translation initiation. In Ramos lymphoma cell lines, which are dependent on MYC overexpression, mutations in the HLH motif greatly reduce MYC expression, impede proliferation and sensitize cells to anti-cancer compounds. These results reveal the potential of the EIF3A HLH motif in eIF3 as a promising chemotherapeutic target.SummaryThe Helix Loop Helix motif of EIF3A controls translation of a small set of oncogenic cellular transcripts, includingMYC, and modulates the function of translation initiation factor EIF4A1 during translation initiation on select mRNAs.

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