Regulation of Unr expression by 5'- and 3'-untranslated regions of its mRNA through modulation of stability and IRES mediated translation

RNA Biol. Jul-Sep 2005;2(3):e27-35. Epub 2005 Jul 23.


Unr (upstream of N-ras) is a cytoplasmic RNA-binding protein that can act as a regulator of mRNA stability and IRES-mediated translation. Unr, a member of the cold-shock domain (CSD) protein super-family, is ubiquitously expressed, with variable abundance, in different tissues or during embryonic development. Prokaryotic and eukaryotic cold-shock protein expression is highly regulated at both the transcriptional and post-transcriptional levels. Here we analyzed the role of the 5'- and 3'-untranslated regions (UTR) of unr mRNA in post-transcriptional regulation of Unr expression. We show that, in vitro, unr 3'-UTR specifically destabilizes unr transcripts. Accordingly, in vivo, the half-life of unr messages deleted of noncoding regions is increased by approximately 3.6 fold, resulting in an enhanced steady-state level of Unr protein. We also show that the 5'-UTR exhibits IRES activity both when translated in vitro and in transiently transfected cells. This IRES activity displays cell type specificity with a higher efficiency in HeLa and HuH7 than in ES cells. Moreover, Unr IRES activity was higher in unr(-/-) than in unr(+/+) ES cells, indicating that Unr negatively regulates its own IRES activity. Our studies further reveal that Unr specifically interacts with its own mRNAs in vivo. These results suggest that a feedback control of mRNA translation is involved in regulating Unr expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions / physiology*
  • 5' Untranslated Regions / physiology*
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites / physiology
  • Cell Line
  • Gene Expression Regulation / physiology*
  • Mice
  • Molecular Sequence Data
  • Poly(A)-Binding Proteins / biosynthesis
  • Poly(A)-Binding Proteins / genetics*
  • RNA Stability / physiology*
  • RNA, Messenger / physiology*


  • 3' Untranslated Regions
  • 5' Untranslated Regions
  • Poly(A)-Binding Proteins
  • RNA, Messenger
  • UNR protein, mouse