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Related Concept Videos

Initiation of Translation02:33

Initiation of Translation

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...
Initiation of Translation02:33

Initiation of Translation

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...
Improving Translational Accuracy02:07

Improving Translational Accuracy

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...
Leaky Scanning02:28

Leaky Scanning

During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA.  Marilyn Kozak discovered that the sequence RCCAUGG (where R stands for...
Eukaryotic Transcription Activators02:42

Eukaryotic Transcription Activators

Transcription activators are proteins that promote the transcription of genes from DNA to RNA. In most cases, these proteins contain two separate domains ‒ a domain that binds to DNA and a domain for activating transcription; however, in some cases, a single domain is responsible for both binding and activation of transcription, as seen in the glucocorticoid receptor and MyoD.
The binding domains are capable of recognizing and interacting with regulatory sequences on the DNA. These domains are...
Transcription Elongation Factors02:35

Transcription Elongation Factors

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.
The transcription elongation is regulated via pausing of RNA polymerase on several occasions during transcription. In bacteria, these halts are necessary because the transcription of DNA into mRNA is coupled to the translation of that mRNA into a...

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Related Experiment Video

Updated: May 31, 2026

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
08:47

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells

Published on: May 1, 2020

eIF5 is a dual function GAP and GDI for eukaryotic translational control.

Martin D Jennings1, Graham D Pavitt

  • 1Faculty of Life Sciences; The University of Manchester; Manchester UK.

Small Gtpases
|June 21, 2011
PubMed
Summary

The eukaryotic translation initiation factor eIF5 acts as both a GAP and a GDI, a dual role crucial for regulating protein synthesis via eIF2 phosphorylation. This discovery offers new insights into translation control mechanisms.

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Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

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Related Experiment Videos

Last Updated: May 31, 2026

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
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Published on: May 1, 2020

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Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells
14:29

Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

Published on: December 25, 2021

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • The eukaryotic translation initiation factor 5 (eIF5) was previously known for its GTPase accelerating protein (GAP) activity.
  • Regulation of protein synthesis is a fundamental cellular process with implications for various biological phenomena.

Purpose of the Study:

  • To elucidate the novel regulatory functions of eIF5 beyond its established GAP activity.
  • To investigate the role of eIF5 as a GDP dissociation inhibitor (GDI) in eukaryotic translation.
  • To understand the critical involvement of eIF5's GDI function in the regulation of protein synthesis through eIF2α phosphorylation.

Main Methods:

  • Biochemical assays to characterize the GTPase activity of eIF5.
  • In vitro reconstitution assays to study translation initiation.
  • Phosphorylation assays to analyze the impact on eIF2α.
  • Genetic studies in eukaryotic systems.

Main Results:

  • Demonstrated that eIF5 possesses a dual regulatory function, acting as both a GAP and a GDI.
  • Identified eIF5's GDI activity as essential for the proper regulation of protein synthesis.
  • Established a critical link between eIF5's GDI function and the phosphorylation of eIF2α at serine 51.
  • Highlighted the broad significance of these findings due to the ubiquitous nature of eIF2 phosphorylation in translational control.

Conclusions:

  • eIF5 exhibits a previously unrecognized dual role as both a GAP and a GDI, significantly impacting translation initiation.
  • The GDI function of eIF5 is indispensable for the precise control of protein synthesis, particularly in response to eIF2α phosphorylation.
  • These findings suggest conserved regulatory mechanisms between translation factors and GTPases, offering a unified view of cellular regulation.