Wheat germ translation initiation factor eIF4B affects eIF4A and eIFiso4F helicase activity by increasing the ATP binding affinity of eIF4A

It has been proposed that, during translational initiation, structures in the 5' untranslated region of mRNA are unwound. eIF4A, a member of the DEAD box family of proteins (those that contain a DEAD amino acid sequence), separately or in conjunction with other eukaryotic initiation factors, utilizes the energy from ATP hydrolysis to unwind these structures. As a step in defining the mechanism of helicase activity in the wheat germ protein synthesis system, we have utilized direct fluorescence measurements, ATPase assays, and helicase assays. The RNA duplex unwinding activity of wheat germ eIF4A is similar to other mammalian systems; however, eIF4F or eIFiso4F is required, probably because of the low binding affinity of wheat germ eIF4A for mRNA. Direct ATP binding measurements showed that eIF4A had a higher binding affinity for ADP than ATP, resulting in a limited hydrolysis and procession along the RNA in the helicase assay. The addition of eIF4B resulted in a change in binding affinity for ATP, increasing it almost 10-fold while the ADP binding affinity was approximately the same. The data presented in this paper suggest that eIF4F or eIFiso4F acts to position the eIF4A and stabilize the interaction with mRNA. ATP produces a conformational change which allows a limited unwinding of the RNA duplex. The binding of eIF4B either prior to or after hydrolysis allows for increased affinity for ATP and for the cycle of conformational changes to proceed, resulting in further unwinding and processive movement along the mRNA.     

Further characterization of the helicase activity of eIF4A. Substrate specificity

Eukaryotic initiation factor (eIF) 4A is the archetypal member of the DEAD box family of RNA helicases and is proposed to unwind structures in the 5'-untranslated region of mRNA to facilitate binding of the 40 S ribosomal subunit. The helicase activity of eIF4A has been further characterized with respect to substrate specificity and directionality. Results confirm that the initial rate and amplitude of duplex unwinding by eIF4A is dependent on the overall stability, rather than the length or sequence, of the duplex substrate. eIF4A helicase activity is minimally dependent on the length of the single-stranded region adjacent to the double-stranded region of the substrate. Interestingly, eIF4A is able to unwind blunt-ended duplexes. eIF4A helicase activity is also affected by substitution of 2'-OH (RNA) groups with 2'-H (DNA) or 2'-methoxyethyl groups. These observations, taken together with results from competitive inhibition experiments, suggest that eIF4A may interact directly with double-stranded RNA, and recognition of helicase substrates occurs via chemical and/or structural features of the duplex. These results allow for refinement of a previously proposed model for the mechanism of action of eIF4A helicase activity.     

Duplex unwinding and ATPase activities of the DEAD-box helicase eIF4A are coupled by eIF4G and eIF4B

Eukaryotic initiation factor (eIF) 4A is a DEAD-box helicase that stimulates translation initiation by unwinding mRNA secondary structure. The accessory proteins eIF4G, eIF4B, and eIF4H enhance the duplex unwinding activity of eIF4A, but the extent to which they modulate eIF4A activity is poorly understood. Here, we use real-time fluorescence assays to determine the kinetic parameters of duplex unwinding and ATP hydrolysis by these initiation factors. To ensure efficient duplex unwinding, eIF4B and eIF4G cooperatively activate the duplex unwinding activity of eIF4A. Our data reveal that eIF4H is much less efficient at stimulating eIF4A unwinding activity than eIF4B, implying that eIF4H is not able to completely substitute for eIF4B in duplex unwinding. By monitoring unwinding and ATPase assays under identical conditions, we demonstrate that eIF4B couples the ATP hydrolysis cycle of eIF4A with strand separation, thereby minimizing nonproductive unwinding events. Using duplex substrates with altered GC contents but similar predicted thermal stabilities, we further show that the rate of formation of productive unwinding complexes is strongly influenced by the local stability per base pair, in addition to the stability of the entire duplex. This finding explains how a change in the GC content of a hairpin is able to influence translation initiation while maintaining the overall predicted thermal stability.     

Biochemical and kinetic characterization of the RNA helicase activity of eukaryotic initiation factor 4A

Eukaryotic initiation factor (eIF) 4A is the prototypic member of the DEAD box family of proteins and has been proposed to act as an RNA helicase to unwind secondary structure in the 5'-untranslated region of eukaryotic mRNAs. Previous studies have shown that the RNA helicase activity of eIF4A is dependent on the presence of a second initiation factor, eIF4B. In this report, eIF4A has been demonstrated to function independently of eIF4B as an ATP-dependent RNA helicase. The biochemical and kinetic properties of this activity were examined. By using a family of RNA duplexes with an unstructured single-stranded region followed by a duplex region of increasing length and stability, it was observed that the initial rate of duplex unwinding decreased with increasing stability of the duplex. Furthermore, the maximum amount of duplex unwound also decreased with increasing stability. Results suggest that eIF4A acts in a non-processive manner. eIF4B and eIF4H were shown to stimulate the helicase activity of eIF4A, allowing eIF4A to unwind longer, more stable duplexes with both an increase in initial rate and maximum amount of duplex unwound. A simple kinetic model is proposed to explain the mechanism by which eIF4A unwinds RNA duplex structures in an ATP-dependent manner.     

A region rich in aspartic acid, arginine, tyrosine, and glycine (DRYG) mediates eukaryotic initiation factor 4B (eIF4B) self-association and interaction with eIF3.

The binding of mRNA to the ribosome is mediated by eukaryotic initiation factors eukaryotic initiation factor 4F (eIF4F), eIF4B, eIF4A, and eIF3, eIF4F binds to the mRNA cap structure and, in combination with eIF4B, is believed to unwind the secondary structure in the 5' untranslated region to facilitate ribosome binding. eIF3 associates with the 40S ribosomal subunit prior to mRNA binding. eIF4B copurifies with eIF3 and eIF4F through several purification steps, suggesting the involvement of a multisubunit complex during translation initiation. To understand the mechanism by which eIF4B promotes 40S ribosome binding to the mRNA, we studied its interactions with partner proteins by using a filter overlay (protein-protein [far Western]) assay and the two-hybrid system. In this report, we show that eIF4B self-associates and also interacts directly with the p170 subunit of eIF3. A region rich in aspartic acid, arginine, tyrosine, and glycine, termed the DRYG domain, is sufficient for self-association of eIF4B, both in vitro and in vivo, and for interaction with the p170 subunit of eIF3. These experiments suggest that eIF4B participates in mRNA-ribosome binding by acting as an intermediary between the mRNA and eIF3, via a direct interaction with the p170 subunit of eIF3.     

Specific domains in yeast translation initiation factor eIF4G strongly bias RNA unwinding activity of the eIF4F complex toward duplexes with 5'-overhangs

During eukaryotic translation initiation, the 43 S ribosomal pre-initiation complex is recruited to the 5'-end of an mRNA through its interaction with the 7-methylguanosine cap, and it subsequently scans along the mRNA to locate the start codon. Both mRNA recruitment and scanning require the removal of secondary structure within the mRNA. Eukaryotic translation initiation factor 4A is an essential component of the translational machinery thought to participate in the clearing of secondary structural elements in the 5'-untranslated regions of mRNAs. eIF4A is part of the 5'-7-methylguanosine cap-binding complex, eIF4F, along with eIF4E, the cap-binding protein, and the scaffolding protein eIF4G. Here, we show that Saccharomyces cerevisiae eIF4F has a strong preference for unwinding an RNA duplex with a single-stranded 5'-overhang versus the same duplex with a 3'-overhang or without an overhang. In contrast, eIF4A on its own has little RNA substrate specificity. Using a series of deletion constructs of eIF4G, we demonstrate that its three previously elucidated RNA binding domains work together to provide eIF4F with its 5'-end specificity, both by promoting unwinding of substrates with 5'-overhangs and inhibiting unwinding of substrates with 3'-overhangs. Our data suggest that the RNA binding domains of eIF4G provide the S. cerevisiae eIF4F complex with a second mechanism, in addition to the eIF4E-cap interaction, for directing the binding of pre-initiation complexes to the 5'-ends of mRNAs and for biasing scanning in the 5' to 3' direction.     

RNA unwinding in translation: assembly of helicase complex intermediates comprising eukaryotic initiation factors eIF-4F and eIF-4B.

Ribosome binding to mRNA requires the concerted action of three initiation factors, eIF-4A, eIF-4B, and eIF-4F, and the hydrolysis of ATP in a mechanism that is not well understood. Several lines of evidence support a model by which these factors bind to the 5' end of mRNA and unwind proximal secondary structure, thus allowing 40S ribosomal subunits to bind. We have previously used an unwinding assay to demonstrate that eIF-4A or eIF-4F in combination with eIF-4B functions as an RNA helicase. To elucidate the molecular mechanism of RNA unwinding, we used a mobility shift electrophoresis assay which allows the simultaneous analysis of unwinding and complex formation between these factors and RNA. eIF-4F forms a stable complex (complex A) with duplex RNA in the absence of ATP. Addition of eIF-4B results in the formation of a second complex (complex B) of slower mobility in the gel. In the presence of ATP, both complexes dissociate, concomitant with the unwinding of the duplex RNA. We present evidence to suggest that unwinding occurs in a processive as opposed to distributive manner. Thus, we conclude that helicase complexes that are formed in the absence of ATP on duplex RNA translocate processively along the RNA in an ATP-dependent reaction and melt secondary structure. These helicase complexes therefore represent intermediates in the unwinding process of mRNA that could precede ribosome binding.     

eIF4B,eIF4G and RNA regulate eIF4A activity in translation initiation by modulating the eIF4A conformational cycle

Eukaryotic translation initiation factor eIF4A is a DEAD-box helicase that resolves secondary structure elements in the 5''-UTR of mRNAs during ribosome scanning. Its RNA-stimulated ATPase and ATP-dependent helicase activities are enhanced by other translation initiation factors, but the underlying mechanisms are unclear. DEAD-box proteins alternate between open and closed conformations during RNA unwinding. The transition to the closed conformation is linked to duplex destabilization. eIF4A is a special DEAD-box protein that can adopt three different conformations, an open state in the absence of ligands, a half-open state stabilized by the translation initiation factor eIF4G and a closed state in the presence of eIF4G and eIF4B. We show here that eIF4A alone does not measurably sample the closed conformation. The translation initiation factors eIF4B and eIF4G accelerate the eIF4A conformational cycle. eIF4G increases the rate of closing more than the opening rate, and eIF4B selectively increases the closing rate. Strikingly, the rate constants and the effect of eIF4B are different for different RNAs, and are related to the presence of single-stranded regions. Modulating the kinetics of the eIF4A conformational cycle is thus central for the multi-layered regulation of its activity, and for its role as a regulatory hub in translation initiation.     

eIF4B and eIF4G Jointly Stimulate eIF4A ATPase and Unwinding Activities by Modulation of the eIF4A Conformational Cycle

Eukaryotic translation initiation factor 4A (eIF4A) is a DEAD-box protein that participates in translation initiation. As an ATP-dependent RNA helicase, it is thought to resolve secondary structure elements from the 5′-untranslated region of mRNAs to enable ribosome scanning. The RNA-stimulated ATPase and ATP-dependent helicase activities of eIF4A are enhanced by auxiliary proteins, but the underlying mechanisms are still largely unknown. Here, we have dissected the effect of eIF4B and eIF4G on eIF4A RNA-dependent ATPase- and RNA helicase activities and on eIF4A conformation. We show for the first time that yeast eIF4B, like its mammalian counterpart, can stimulate RNA unwinding by eIF4A, although it does not affect the eIF4A conformation. The eIF4G middle domain enhances this stimulatory effect and promotes the formation of a closed eIF4A conformation in the presence of ATP and RNA. The closed state of eIF4A has been inferred but has not been observed experimentally before. eIF4B and eIF4G jointly stimulate ATP hydrolysis and RNA unwinding by eIF4A and favor the formation of the closed eIF4A conformer. Our results reveal distinct functions of eIF4B and eIF4G in synergistically stimulating the eIF4A helicase activity in the mRNA scanning process.     

Wheat germ poly(A)-binding protein increases the ATPase and the RNA helicase activity of translation initiation factors eIF4A, eIF4B, and eIF-iso4F

Recent studies demonstrated that wheat germ poly(A)-binding protein (PABP) interacted with translation eukaryotic initiation factor (eIF)-iso4G and eIF4B, and these interactions increased the poly(A) binding activity of PABP (Le, H., Tanguay, R. L., Balasta, M. L., Wei, C. C., Browning, K. S., Metz, A. M., Goss, D. J., and Gallie, D. R. (1997) J. Biol. Chem. 272, 16247-16255) and the cap binding activity of eIF-iso4F (Wei, C. C., Balasta, M. L., Ren, J., and Goss, D. J. (1998) Biochemistry 37, 1910-1916). We report here that the interaction between PABP and eIF-iso4G has a substantial effect on the ATPase activity and RNA helicase activity of (eIF4A + eIF4B + eIF-iso4F) complex. ATPase kinetic assays show, in the presence of poly(U), PABP can increase the parameter (k(cat)/K(m)) by 3.5-fold with a 2-fold decrease of K(m) for the (eIF4A + eIF-iso4F) complex. In the presence of globin messenger RNA, the ATPase activity of the complex (eIF4A + eIF-iso4F) was increased 2-fold by the presence of PABP. RNA helicase assays demonstrated that the presence of PABP enhanced the RNA duplex unwinding activity of the initiation factor complex. These results suggest that, in terms of the scanning model of translation initiation, PABP may enhance the mRNA scanning rate of the complex formed by eIF4A, eIF4B, and eIF4F or eIF-(iso)4F and increase the rate of translation.     

The domains of yeast eIF4G,eIF4E and the cap fine-tune eIF4A activities through an intricate network of stimulatory and inhibitory effects

Translation initiation in eukaryotes starts with the recognition of the mRNA 5′-cap by eIF4F, a hetero-trimeric complex of eIF4E, the cap-binding protein, eIF4A, a DEAD-box helicase, and eIF4G, a scaffold protein. eIF4G comprises eIF4E- and eIF4A-binding domains (4E-BD, 4A-BD) and three RNA-binding regions (RNA1–RNA3), and interacts with eIF4A, eIF4E, and with the mRNA. Within the eIF4F complex, the helicase activity of eIF4A is increased. We showed previously that RNA3 of eIF4G is important for the stimulation of the eIF4A conformational cycle and its ATPase and helicase activities. Here, we dissect the interplay between the eIF4G domains and the role of the eIF4E/cap interaction in eIF4A activation. We show that RNA2 leads to an increase in the fraction of eIF4A in the closed state, an increased RNA affinity, and faster RNA unwinding. This stimulatory effect is partially reduced when the 4E-BD is present. eIF4E binding to the 4E-BD then further inhibits the helicase activity and closing of eIF4A, but does not affect the RNA-stimulated ATPase activity of eIF4A. The 5′-cap renders the functional interaction of mRNA with eIF4A less efficient. Overall, the activity of eIF4A at the 5′-cap is thus fine-tuned by a delicately balanced network of stimulatory and inhibitory interactions.     

Bidirectional RNA helicase activity of eucaryotic translation initiation factors 4A and 4F.

The mechanism of ribosome binding to eucaryotic mRNAs is not well understood, but it requires the participation of eucaryotic initiation factors eIF-4A, eIF-4B, and eIF-4F and the hydrolysis of ATP. Evidence has accumulated in support of a model in which these initiation factors function to unwind the 5'-proximal secondary structure in mRNA to facilitate ribosome binding. To obtain direct evidence for initiation factor-mediated RNA unwinding, we developed a simple assay to determine RNA helicase activity, and we show that eIF-4A or eIF-4F, in combination with eIF-4B, exhibits helicase activity. A striking and unprecedented feature of this activity is that it functions in a bidirectional manner. Thus, unwinding can occur either in the 5'-to-3' or 3'-to-5' direction. Unwinding in the 5'-to-3' direction by eIF-4F (the cap-binding protein complex), in conjunction with eIF-4B, was stimulated by the presence of the RNA 5' cap structure, whereas unwinding in the 3'-to-5' direction was completely cap independent. These results are discussed with respect to cap-dependent versus cap-independent mechanisms of ribosome binding to eucaryotic mRNAs.     

Interaction between the NH2-terminal domain of eIF4A and the central domain of eIF4G modulates RNA-stimulated ATPase activity

The eukaryotic translation factor 4A (eIF4A) is a member of DEA(D/H)-box RNA helicase family, a diverse group of proteins that couples ATP hydrolysis to RNA binding and duplex separation. eIF4A participates in the initiation of translation by unwinding secondary structure in the 5'-untranslated region of mRNAs and facilitating scanning by the 40 S ribosomal subunit for the initiation codon. eIF4A alone has only weak ATPase and helicase activities, but these are stimulated by eIF4G, eIF4B, and eIF4H. eIF4G has two eIF4A-binding sites, one in the central domain (cp(C3)) and one in the COOH-terminal domain (cp(C2)). In the current work, we demonstrate that these two eIF4G domains have different effects on the RNA-stimulated ATPase activity of eIF4A. cp(C3) stimulates ATP-hydrolytic efficiency by about 40-fold through two mechanisms: lowering K(m)(RNA) by 10-fold and raising k(cat) by 4-fold. cp(C3) also stimulates RNA cross-linking to eIF4A in an ATP-independent manner. Studies with eIF4G and eIF4A variants suggest a model by which cp(C3) alters the conformation of the catalytic site to favor RNA binding. cp(C2) does not stimulate ATPase activity and furthermore increases both K(m)(ATP) (at saturating RNA concentrations) and K(m)(RNA) (at subsaturating ATP concentrations). Both cp(C3) and cp(C2) directly interact with the NH(2)-terminal domain of eIF4A, which possesses conserved ATP- and oligonucleotide-binding motifs, but not with the COOH-terminal domain.     

The Eukaryotic Initiation Factor (eIF) 4G HEAT Domain Promotes Translation Re-initiation in Yeast Both Dependent on and Independent of eIF4A mRNA Helicase

Translation re-initiation provides the molecular basis for translational control of mammalian ATF4 and yeast GCN4 mediated by short upstream open reading (uORFs) in response to eIF2 phosphorylation. eIF4G is the major adaptor subunit of eIF4F that binds the cap-binding subunit eIF4E and the mRNA helicase eIF4A and is also required for re-initiation in mammals. Here we show that the yeast eIF4G2 mutations altering eIF4E- and eIF4A-binding sites increase re-initiation at GCN4 and impair recognition of the start codons of uORF1 or uORF4 located after uORF1. The increase in re-initiation at GCN4 was partially suppressed by increasing the distance between uORF1 and GCN4, suggesting that the mutations decrease the migration rate of the scanning ribosome in the GCN4 leader. Interestingly, eIF4E overexpression suppressed both the phenotypes caused by the mutation altering eIF4E-binding site. Thus, eIF4F is required for accurate AUG selection and re-initiation also in yeast, and the eIF4G interaction with the mRNA-cap appears to promote eIF4F re-acquisition by the re-initiating 40 S subunit. However, eIF4A overexpression suppressed the impaired AUG recognition but not the increase in re-initiation caused by the mutations altering eIF4A-binding site. These results not only provide evidence that mRNA unwinding by eIF4A stimulates start codon recognition, but also suggest that the eIF4A-binding site on eIF4G made of the HEAT domain stimulates the ribosomal scanning independent of eIF4A. Based on the RNA-binding activities identified within the unstructured segments flanking the eIF4G2 HEAT domain, we discuss the role of the HEAT domain in scanning beyond loading eIF4A onto the pre-initiation complex.     

A role for eIF4E and eIF4E-transporter in targeting mRNPs to mammalian processing bodies

mRNP remodeling events required for the transition of an mRNA from active translation to degradation are currently poorly understood. We identified protein factors potentially involved in this transition, which are present in mammalian P bodies, cytoplasmic foci enriched in 5' --> 3' mRNA degrading enzymes. We demonstrate that human P bodies contain the cap-binding protein eIF4E and the related factor eIF4E-transporter (eIF4E-T), suggesting novel roles for these proteins in targeting mRNAs for 5' --> 3' degradation. Furthermore, fluorescence resonance energy transfer (FRET) studies indicate that eIF4E interacts with eIF4E-T and the putative DEAD box helicase rck/p54 in the P bodies in vivo. RNAi-mediated knockdowns revealed that a subset of P body factors, including eIF4E-T, LSm1, rck/p54, and Ccr4 are required for the accumulation of each other and eIF4E in P bodies. In addition, treatment of HeLa cells with cycloheximide, which inhibits translation, revealed that mRNA is also required for accumulation of mRNA degradation factors in P bodies. In contrast, knockdown of the decapping enzyme Dcp2, which initiates the actual 5' --> 3' mRNA degradation did not abolish P body formation, indicating it first functions after mRNPs have been targeted to these cytoplasmic foci. These data support a model in which mRNPs undergo several successive steps of remodeling and/or 3' trimming until their composition or structural organization promotes their accumulation in P bodies.     

Eukaryotic Translation Initiation Factor 4AIII (eIF4AIII) Is Functionally Distinct from eIF4AI and eIF4AII

Eukaryotic initiation factor 4A (eIF4A) is an RNA-dependent ATPase and ATP-dependent RNA helicase that is thought to melt the 5' proximal secondary structure of eukaryotic mRNAs to facilitate attachment of the 40S ribosomal subunit. eIF4A functions in a complex termed eIF4F with two other initiation factors (eIF4E and eIF4G). Two isoforms of eIF4A, eIF4AI and eIF4AII, which are encoded by two different genes, are functionally indistinguishable. A third member of the eIF4A family, eIF4AIII, whose human homolog exhibits 65% amino acid identity to human eIF4AI, has also been cloned from Xenopus and tobacco, but its function in translation has not been characterized. In this study, human eIF4AIII was characterized biochemically. While eIF4AIII, like eIF4AI, exhibits RNA-dependent ATPase activity and ATP-dependent RNA helicase activity, it fails to substitute for eIF4AI in an in vitro-reconstituted 40S ribosome binding assay. Instead, eIF4AIII inhibits translation in a reticulocyte lysate system. In addition, whereas eIF4AI binds independently to the middle and carboxy-terminal fragments of eIF4G, eIF4AIII binds to the middle fragment only. These functional differences between eIF4AI and eIF4AIII suggest that eIF4AIII might play an inhibitory role in translation under physiological conditions.     

Escherichia coli PriA helicase: fork binding orients the helicase to unwind the lagging strand side of arrested replication forks

Escherichia coli PriA is a primosome assembly protein with 3' to 5' helicase activity whose apparent function is to promote resumption of DNA synthesis following replication-fork arrest. Here, we describe how initiation of helicase activity on DNA forks is influenced by both fork structure and by single-strand DNA-binding protein. PriA could recognize and unwind forked substrates where one or both arms were primarily duplex, and PriA required a small (two bases or larger) single-stranded gap at the fork in order to initiate unwinding. The helicase was most active on substrates with a duplex lagging-strand arm and a single-stranded leading-strand arm. On this substrate, PriA was capable of translocating on either the leading or lagging strands to unwind the duplex ahead of the fork or the lagging-strand duplex, respectively. Fork-specific binding apparently orients the helicase domain to unwind the lagging-strand duplex. Binding of single-strand-binding protein to forked templates could inhibit unwinding of the duplex ahead of the fork but not unwinding of the lagging-strand duplex or translocation on the lagging-strand template. While single-strand-binding protein could inhibit binding of PriA to the minimal, unforked DNA substrates, it could not inhibit PriA binding to forked substrates. In the cell, single-strand-binding protein and fork structure may direct PriA helicase to translocate along the lagging-strand template of forked structures such that the primosome is specifically assembled on that DNA strand.     

eIF4B controls survival and proliferation and is regulated by proto-oncogenic signaling pathways

Messenger RNA translation or protein synthesis, is a fundamental biological process affecting cell growth, survival and proliferation. Initiation is the rate limiting and hence the most regulated step of translation. In eukaryotes, translation initiation is facilitated by multiple protein factors collectively called eIFs (for eukaryotic translation initiation factors). The complex consisting of the eIF4 group factors including the mRNA cap-binding eIF4E protein, large scaffolding protein eIF4G and RNA helicase eIF4A is assisted by the eIF4B co-factor to unwind local secondary structures and create a ribosome landing pad on mRNA. Recruitment of the ribosome and augmentation in the mRNA scanning process culminates in the positioning of the ribosome over the start codon. Deregulated translational control is believed to play an important role in oncogenic transformation. Indeed, many eIFs are bona fide proto-oncogenes. In many types of human cancers, eIFs are either overexpressed or ectopically activated by Ras-MAPK and PI3K-mTOR signaling cascades, resulting in increased survival and accelerated proliferation. In this review we will analyze the bulk of data describing eIF4B and its role in cell survival and proliferation. Recent studies have shown that eIF4B is phosphorylated and activated by Ras-MAPK and PI3K-mTOR signaling cascades. In addition, eIF4B regulates translation of proliferative and pro-survival mRNAs. Moreover, eIF4B depletion in cancer cells attenuates proliferation, sensitizes them to genotoxic stress-driven apoptosis. Taken together, these findings identify eIF4B as a potential target for development of anti-cancer therapies.Key words: eIF4B, translation, signaling, structured 5′UTR, helicase activity, survival, proliferation, apoptosis