ABSTRACT
Of critical importance in the stress response is the post-transcriptional control of the expression of important genes involved in the control of cell survival and apoptosis. Here we report that miR-19, an oncogenic component of the miR-17-92/Oncomir-1 microRNA polycistron, regulates the expression of Ras homolog B (RhoB) in keratinocytes upon exposure to ultraviolet (UV) radiation. Strikingly, we could not find any evidence for deregulated expression of miR-19 during UV treatment. However, we show that miR-19-mediated regulation of antiapoptotic RhoB expression requires the binding of human antigen R (HuR), an AU-rich element binding protein, to the 3'-untranslated region of the rhoB mRNA. We propose that the loss of the interdependent binding between HuR and miR-19 to the rhoB mRNA upon UV exposure relieves this mRNA from miR-19-dependent inhibition of translation and contributes to the apoptotic response.
Subject(s)
Apoptosis/radiation effects , ELAV Proteins/metabolism , MicroRNAs/metabolism , RNA, Messenger/metabolism , Ultraviolet Rays , rhoB GTP-Binding Protein/metabolism , 3' Untranslated Regions , Binding Sites , Cell Line , ELAV Proteins/antagonists & inhibitors , ELAV Proteins/genetics , Humans , Luciferases, Firefly/genetics , Luciferases, Firefly/metabolism , Protein Binding , RNA Interference , RNA, Small Interfering/metabolism , rhoB GTP-Binding Protein/geneticsABSTRACT
⢠Characteristic sterols of transformed carrot (Daucus carota) and chicory (Cichorium intybus) roots colonized by different strains of arbuscular mycorrhizal (AM) fungi were identified. ⢠Sterols were extracted, analysed and identified by gas chromatography/mass spectrometry (GC-MS) from monoxenic cultures of mycorrhizal and nonmycorrhizal roots. After colonization by Glomus intraradices, Glomus proliferum and Glomus sp., carrot and chicory roots exhibited a significantly higher 24-methyl/methylene sterol content. A correlation was established between the content of the sum of 24-methyl cholesterol, 24-methylene cholesterol and 24-methyl desmosterol. ⢠This study clearly established that the increment of these characteristic sterols is an appropriate indicator of colonization by AM fungi of transformed roots. ⢠Metabolic origin and specificity of these sterols in mycorrhizal roots was researched. The 24-methyl/methylene sterol increase was observed only when the interaction between fungus and plant was completely established and the fungus was present inside the roots.
