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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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Improving Translational Accuracy02:07

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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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Leaky Scanning02:28

Leaky Scanning

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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...
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Transcription Elongation Factors02:35

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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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Translation in Prokaryotes01:29

Translation in Prokaryotes

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Prokaryote translation is a complex, highly coordinated process that converts genetic information from mRNA into functional proteins. It involves three stages: initiation, elongation, and termination, each facilitated by specific molecular components.Initiation of TranslationThe process begins with the assembly of the ribosomal subunits and initiation factors on the mRNA. In bacteria, the 30S ribosomal subunit recognizes the Shine-Dalgarno sequence in the mRNA, a conserved region upstream of...
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Regulated mRNA Transport02:22

Regulated mRNA Transport

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In eukaryotes, transcription and translation are compartmentalized; an mRNA is first synthesized in the nucleus and then selectively transported to the cytoplasm for protein synthesis. Before transport, a pre-mRNA undergoes several steps of post-transcriptional modifications including splicing, 5' capping, and the addition of a poly-adenine tail. Various proteins bind to the pre-mRNA during these modifications. The mRNA transport takes place with the help of multiple proteins playing...
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Updated: Sep 13, 2025

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
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Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs

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eIF1 and eIF5 dynamically control translation start site fidelity.

Rosslyn Grosely1, Carlos Alvarado1, Ivaylo P Ivanov2

  • 1Dept. of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.

Nature Structural & Molecular Biology
|July 28, 2025
PubMed
Summary
This summary is machine-generated.

Human translation initiation relies on start site recognition. This study reveals how initiation factors eIF1 and eIF5 compete to control start site selection, ensuring accurate translation and impacting health and disease.

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Related Experiment Videos

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Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
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Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Accurate translation initiation is crucial for protein synthesis in humans.
  • While AUG is the canonical start codon, non-AUG codons are also recognized, albeit less efficiently.
  • Initiation factors eukaryotic initiation factor 1 (eIF1) and eIF5 play key roles in start site selection, but their precise mechanisms remain unclear.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which eIF1 and eIF5 regulate translation start site selection.
  • To understand how these factors differentiate between canonical AUG and non-AUG start sites.
  • To reveal the dynamic interplay between eIF1 and eIF5 in controlling translation fidelity.

Main Methods:

  • Utilized real-time single-molecule assays.
  • Employed an in vitro reconstituted human translation system.
  • Confirmed findings in human cells.

Main Results:

  • eIF1 binds initiation complexes in two distinct modes: stable during scanning and transiently after start site recognition.
  • eIF5 binding is required to terminate eIF1 rebinding, enabling translation-competent ribosome formation.
  • Non-AUG start sites alter eIF1 and eIF5 binding dynamics, leading to initiation blockage.

Conclusions:

  • eIF1 and eIF5 directly compete for binding to translation initiation complexes.
  • Their dynamic interaction precisely tunes the fidelity of start site recognition.
  • Dysregulation of this process has significant implications for human health and disease.