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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...
Termination of Translation01:44

Termination of Translation

The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the site where the peptide bond is formed - and a large, internal, water-filled tube through which the nascent polypeptide moves. This latter structure is called the Peptide Exit Tunnel, and it begins at the PTC and spans the body of the large ribosomal subunit. During translation, as the nascent polypeptide chain is synthesized, it passes through...
Termination of Translation01:44

Termination of Translation

The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the site where the peptide bond is formed - and a large, internal, water-filled tube through which the nascent polypeptide moves. This latter structure is called the Peptide Exit Tunnel, and it begins at the PTC and spans the body of the large ribosomal subunit. During translation, as the nascent polypeptide chain is synthesized, it passes through...
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...
Retrovirus Life Cycles01:10

Retrovirus Life Cycles

Retroviruses have a single-stranded RNA genome that undergoes a special form of replication. Once the retrovirus has entered the host cell, an enzyme called reverse transcriptase synthesizes double-stranded DNA from the retroviral RNA genome. This DNA copy of the genome is then integrated into the host’s genome inside the nucleus via an enzyme called integrase. Consequently, the retroviral genome is transcribed into RNA whenever the host’s genome is transcribed, allowing the retrovirus to...

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In Vitro Transcribed RNA-based Luciferase Reporter Assay to Study Translation Regulation in Poxvirus-infected Cells
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Translational termination-re-initiation in viral systems.

Michael L Powell1, T David K Brown, Ian Brierley

  • 1Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK. mlp34@cam.ac.uk

Biochemical Society Transactions
|July 18, 2008
PubMed
Summary

Viruses use termination-dependent re-initiation to control protein expression from polycistronic mRNAs. This mechanism couples upstream and downstream open reading frames (ORFs) for efficient viral protein synthesis.

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Last Updated: Jul 3, 2026

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Published on: May 1, 2019

Xenopus laevis as a Model to Identify Translation Impairment
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Published on: September 27, 2015

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
10:37

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs

Published on: May 10, 2018

Area of Science:

  • Molecular Biology
  • Virology
  • Genetics

Background:

  • Viruses employ diverse strategies to regulate viral protein synthesis from polycistronic mRNAs.
  • Mechanisms like programmed ribosomal frameshifting and stop codon readthrough are established.
  • Termination-dependent re-initiation (stop-start) is an emerging translational control mechanism.

Purpose of the Study:

  • To review the regulation of termination-dependent re-initiation in viral systems.
  • To explore the coupling of upstream and downstream open reading frames (ORFs).
  • To highlight differences in re-initiation mechanisms across prokaryotic, eukaryotic, and viral mRNAs.

Main Methods:

  • Literature review of viral translational control mechanisms.
  • Analysis of mRNA structures and translation initiation/termination signals.
  • Comparative analysis of re-initiation across different biological systems.

Main Results:

  • Termination-dependent re-initiation couples the expression of ORFs.
  • The stop codon of an upstream ORF (uORF) is proximal to the start codon of a downstream ORF.
  • Influenza B virus mRNA provides an example of overlapping stop-start codons.

Conclusions:

  • Termination-dependent re-initiation is a key viral strategy for regulating protein expression.
  • Understanding this mechanism is crucial for comprehending viral gene expression.
  • Comparative analysis reveals conserved and distinct features of re-initiation across life domains.