IRES-dependent translation of egr2 is induced under inflammatory conditions.
Adjusting translation is crucial for cells to rapidly adapt to changing conditions. While pro-proliferative signaling via the PI3K-mTOR-pathway is known to induce cap-dependent translation, stress conditions, such as nutrient deprivation or hypoxia often activate alternative modes of translation, e.g., via internal ribosome entry sites (IRESs). As the effects of inflammatory conditions on translation are only poorly characterized, we aimed at identifying translationally deregulated targets in inflammatory settings. For this purpose, we cocultured breast tumor cells with conditioned medium of activated monocyte-derived macrophages (CM). Polysome profiling and microarray analysis identified early growth response-2 (egr2) to be regulated at the level of translation. Using bicistronic reporter assays, we found that egr2 contains an IRES within its 5' UTR, which facilitated enhanced translation upon CM treatment. We further provide evidence that the activity of egr2-IRES was induced by IL-1β and p38-MAPK signaling. In addition, we identified several potential IRES trans-acting factors (ITAFs) such as polypyrimidine tract binding protein (PTB) and hnRNP-A1 that directly bind to the egr2-5'UTR. In summary, our data provide evidence that egr2 expression is translationally regulated via an IRES element, which is responsive to an inflammatory environment.
Institute of Biochemistry I, Goethe-University Frankfurt, 60590 Frankfurt, Germany.
Daniela
D
Rübsamen
Johanna S
JS
Blees
Kathrin
K
Schulz
Claudia
C
Döring
Martin-Leo
ML
Hansmann
Heinrich
H
Heide
Andreas
A
Weigert
Tobias
T
Schmid
Bernhard
B
Brüne
D001483:Base Sequence; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D051767:Early Growth Response Protein 2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D053583:Interleukin-1beta / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology; D038621:Regulatory Sequences, Ribonucleic Acid / Q000502:physiology*; D012270:Ribosomes / Q000378:metabolism*; D020298:U937 Cells; D015854:Up-Regulation / Q000187:drug effects
C497326:EGR2 protein, human; D051767:Early Growth Response Protein 2; D053583:Interleukin-1beta; D038621:Regulatory Sequences, Ribonucleic Acid