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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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In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl...
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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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Pre-mRNA Processing: Modification of pre-mRNA Ends01:35

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In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
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mRNA Stability and Gene Expression02:51

mRNA Stability and Gene Expression

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The structure and stability of mRNA molecules regulates gene expression, as mRNAs are a key step in the pathway from gene to protein. In eukaryotes, the half-life of mRNA varies from a few minutes up to several days. mRNA stability is essential in growth and development. The absence of the proteins regulating its stability, such as tristetraprolin in mice, can cause systemic issues, including bone marrow overgrowth, inflammation, and autoimmunity.
Cis-acting Elements involved in mRNA stability
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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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Related Experiment Video

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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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Preinitiation Complex Loading onto mRNAs with Long versus Short 5' TLs.

Benjamin Weiss1, Pascale Jaquier-Gubler1, Joseph Alphonsus Curran1,2

  • 1Department of Microbiology and Molecular Medicine, University of Geneva Medical School, 1211 Geneva, Switzerland.

International Journal of Molecular Sciences
|November 11, 2022
PubMed
Summary

The length of the 5' transcript leader (TL) affects ribosome recruitment during translation initiation. Short TLs disrupt eIF4E-cap interactions, while long TLs allow mRNA distribution, impacting translation start site selection.

Keywords:
5′ TLeIF4Etranslation initiation

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Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Translation initiation is crucial for gene expression, involving small ribosome recruitment to mRNA.
  • The preinitiation complex (PIC) assembles on the 5' cap via eIF4F interactions.
  • The 5' transcript leader (TL) length plays a role in scanning and start site recognition.

Purpose of the Study:

  • To investigate the role of 5' transcript leader (TL) length in translation initiation.
  • To analyze how TL length influences the interaction between eIF4E and the 5' cap.
  • To understand the molecular architecture of the PIC-mRNA complex.

Main Methods:

  • In vivo and in vitro analysis of translation initiation.
  • Ribosomal toe-printing to confirm start site positioning.
  • Solid-phase in vitro expression assay to track eIF4E-cap interactions.

Main Results:

  • Translation initiation occurs at AUG codons within 3 nucleotides of the 5' cap.
  • Ribosomes initiate translation from the +1 position.
  • Short TLs disrupt eIF4E-cap interactions, releasing mRNA, while long TLs lead to mRNA distribution.

Conclusions:

  • The 5' TL length is a critical determinant of translation initiation efficiency.
  • Ribosome recruitment dynamics are modulated by TL length, affecting eIF4E-cap complex stability.
  • Findings contribute to understanding mRNA recruitment models in translation.