title: Ubiquitin-dependent mechanism regulates rapid turnover of AU-rich cytokine mRNAs.
abstract: An AU rich element (ARE) in the 3' noncoding region promotes the rapid degradation of mammalian cytokine and proto-oncogene mRNAs, such as tumor necrosis factor-alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF) and c-fos. Destabilization of ARE-mRNAs involves the association of ARE-binding proteins tristetraprolin or AUF1 and proteasome activity, of which the latter has not been characterized. Here, we show that the stability of a model short-lived mRNA containing the GM-CSF ARE was regulated by the level of ubiquitin-conjugating activity in the cell, which links ARE-mRNA decay to proteasome activity. Increased expression of a cytokine-inducible deubiquitinating protein (DUB) that impairs addition of ubiquitin to proteins fully blocked ARE-mRNA decay, whereas increased expression of a DUB that promotes ubiquitin addition to proteins strongly accelerated ARE-mRNA decay. ARE-mRNA turnover was found to be activated by the ubiquitin-addition reaction and blocked by the ubiquitin-removal reaction. Saturation of the ARE-mRNA decay machinery by high levels of ARE-mRNA, which is well established but not understood, was found to be relieved by increased expression of a DUB that promotes ubiquitin addition to proteins. Finally, inhibition of proteasome activity also blocked accelerated ARE-mRNA decay that is mediated by increased ubiquitin recycling. These results demonstrate that both ubiquitinating activity and proteasome activity are essential for rapid turnover of a model cytokine ARE-mRNA containing the GM-CSF ARE.
authors.affiliation: Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Laroia
authors.forename: Bedabrata
authors.initials: B
authors.lastname: Sarkar
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schneider
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D019556:COS Cells; D002460:Cell Line; D017930:Genes, Reporter; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008954:Models, Biological; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry* / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D000199:Actins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D025801:Ubiquitin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor