title: Regulation of Unr expression by 5'- and 3'-untranslated regions of its mRNA through modulation of stability and IRES mediated translation.
abstract: 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.
authors.affiliation: INSERM E362, Université Victor Segalen Bordeaux 2, Bordeaux, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Dormoy-Raclet
authors.forename: Judith
authors.initials: J
authors.lastname: Markovits
authors.forename: Alain
authors.initials: A
authors.lastname: Jacquemin-Sablon
authors.forename: Hélène
authors.initials: H
authors.lastname: Jacquemin-Sablon
mesh_terms: D020413:3' Untranslated Regions / Q000502:physiology*; D020121:5' Untranslated Regions / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000502:physiology; D002460:Cell Line; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D039102:Poly(A)-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D020871:RNA Stability / Q000502:physiology*; D012333:RNA, Messenger / Q000502:physiology*
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; C489441:UNR protein, mouse