Internal Ribosome Entry Sites Tests with Circular mRNAs

  • Chang-you Chen
  • Peter Sarnow
Part of the Methods in Molecular Biology book series (MIMB, volume 77)


It was shown that eukaryotic ribosomes, in contrast to prokaryotic ribosomes, were unable to bind to small circular RNAs (1,2). This finding was a key feature in the scanning model for translational initiation, which postulates that eukaryotic 40S ribosomal subunits enter mRNAs exclusively at their free, capped 5′ ends like beads on a string (3). Subsequently, 40S subunits carrying eukaryotic translation initiation factors and initiator tRNAs are thought to scan the mRNA in a 5′ to 3′ direction until an appropriate AUG codon is encountered that can be used as start site for protein biosynthesis (3). However, this model has been challenged with the discovery of internal ribosome entry site (IRES) elements, present in certain viral and cellular mRNAs, that can mediate translational initiation without prior scanning of the mRNA by 40S sub-units (4, 5, 6, 7, 8, 9).


Sodium Dodecyl Sulfate Internal Ribosome Entry Site Circular RNAs Internal Ribosome Entry Site Element Eukaryotic Ribosome 
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Copyright information

© Humana Press Inc. 1998

Authors and Affiliations

  • Chang-you Chen
    • 1
  • Peter Sarnow
    • 1
  1. 1.Department of Biochemistry, Biophysics, and GeneticsUniversity of Colorado Health Sciences CenterDenver

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