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Related Concept Videos

Initiation of Translation02:33

Initiation of Translation

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Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
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Base complementarity between the three base pairs of mRNA codon and the tRNA anticodon is not a failsafe mechanism. Inaccuracies can range from a single mismatch to no correct base pairing at all. The free energy difference between the correct and nearly correct base pairs can be as small as 3 kcal/ mol. With complementarity being the only proofreading step, the estimated error frequency would be one wrong amino acid in every 100 amino acids incorporated. However, error frequencies observed in...
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Transcription elongation is a dynamic process that alters depending upon the sequence heterogeneity of the DNA being transcribed. Hence, it is not surprising that the elongation complex's composition also varies along the way while transcribing a gene.
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Eukaryotic RNA Polymerases00:58

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RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional similarities. Among the three eukaryotic RNAPs, RNA Polymerase II is most similar to bacterial RNAP in terms of both structural organization and folding topologies of the enzyme subunits. However, these similarities are not reflected in their mechanism of action.
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Related Experiment Video

Updated: Apr 29, 2026

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
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eIF4B, eIF4G and RNA regulate eIF4A activity in translation initiation by modulating the eIF4A conformational cycle.

Ulf Harms1, Alexandra Zoi Andreou1, Airat Gubaev1

  • 1University of Muenster, Institute for Physical Chemistry, Corrensstrasse 30, D-48149 Muenster, Germany.

Nucleic Acids Research
|May 23, 2014
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Summary

Eukaryotic translation initiation factor eIF4A (eIF4A) alone doesn't adopt its closed state. Translation factors eIF4G and eIF4B accelerate its conformational cycle, crucial for regulating translation initiation.

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Area of Science:

  • Molecular biology
  • Biochemistry
  • Structural biology

Background:

  • Eukaryotic translation initiation factor 4A (eIF4A) is a DEAD-box helicase essential for resolving mRNA secondary structures during ribosome scanning.
  • Its RNA-dependent ATPase and helicase activities are modulated by other initiation factors, but the mechanisms remain incompletely understood.
  • DEAD-box proteins cycle through open and closed conformations during RNA unwinding, with closure linked to duplex destabilization.

Purpose of the Study:

  • To investigate the conformational dynamics of eIF4A in the absence and presence of translation initiation factors eIF4G and eIF4B.
  • To elucidate the roles of eIF4G and eIF4B in modulating the conformational cycle of eIF4A.
  • To determine how RNA structure influences the kinetics of eIF4A conformational changes.

Main Methods:

  • Stopped-flow kinetics assays to monitor eIF4A conformational changes.
  • Use of purified recombinant eIF4A, eIF4G, and eIF4B proteins.
  • Employing various RNA substrates with differing secondary structures.

Main Results:

  • eIF4A alone does not significantly populate the closed conformation.
  • Both eIF4G and eIF4B accelerate the eIF4A conformational cycle.
  • eIF4G enhances both closing and opening rates, while eIF4B selectively accelerates the closing rate.
  • The kinetics and eIF4B's effects vary with RNA sequence and the presence of single-stranded regions.

Conclusions:

  • The conformational cycle of eIF4A is regulated by translation initiation factors eIF4G and eIF4B.
  • eIF4B's selective acceleration of the closing rate is RNA-dependent.
  • Modulating eIF4A's conformational kinetics is central to its regulatory role in translation initiation.