The arabidopsis thaliana MHX gene includes an intronic element that boosts translation when localized in a 5′ UTR intron

Tsofit Akua, Orit Shaul

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The mechanisms that underlie the ability of some introns to increase gene expression, a phenomenon called intron-mediated enhancement (IME), are not fully understood. It is also not known why introns localized in the 5′-untrans-lated region (5′ UTR) are considerably longer than downstream eukaryotic introns. It was hypothesized that this extra length results from the presence of some functional intronic elements. However, deletion analyses studies carried out thus far were unable to identify specific intronic regions necessary for IME. Using deletion analysis and a gain-of-function approach, an internal element that considerably increases translational efficiency, without affecting splicing, was identified in the 5′ UTR intron of the Arabidopsis thaliana MHX gene. Moreover, the ability of this element to enhance translation was diminished by a minor downstream shift in the position of introns containing it from the 5′ UTR into the coding sequence. These data suggest that some of the extra length of 5′ UTR introns results from the presence of elements that enhance translation, and, moreover, from the ability of 5′ UTR introns to provide preferable platforms for such elements over downstream introns. The impact of the identified intronic element on translational efficiency was augmented upon removal of neighbouring intronic elements. Interference between different intronic elements had not been reported thus far. This interference may support the bioinformatics-based idea that some of the extra sequence of 5′ UTR introns is also necessary for separating different functional intronic elements.

Original languageEnglish
Pages (from-to)4255-4270
Number of pages16
JournalJournal of Experimental Botany
Issue number14
Early online date4 Sep 2013
StatePublished - Nov 2013

Bibliographical note

Funding Information:
This work was supported by the Israel Science Foundation (grant no. 199/09).


  • 5′ UTR
  • 5′ untranslated region
  • IME
  • Intron-mediated enhancement
  • Leader intron
  • Translational regulation


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