Fragile X-related protein FXR1P regulates proinflammatory cytokine tumor necrosis factor expression at the post-transcriptional level.
Tumor necrosis factor (TNF) is regulated post-transcriptionally by the AU-rich element (ARE) within the 3'-untranslated region of its mRNA. This regulation modulates translational efficacy and mRNA stability. By using a cRNA probe containing the TNF ARE sequence, we screened a macrophage protein expression library and identified FXR1P. Macrophages that we generated from FXR1 knock-out mice had enhanced TNF protein production compared with wild type macrophages following activation. Expression of several other proteins that are regulated by ARE sequences was also affected by FXR1P deficiency. A GFP-ARE reporter that has green fluorescent protein (GFP) expression under control of the 3'-untranslated region of TNF mRNA had enhanced expression in transfected macrophages deficient in FXR1P. Finally, we found that the ablation of FXR1P led to a dramatically enhanced association of the TNF mRNA with polyribosomes demonstrating the important role of FXR1P in the post-transcriptional regulation of TNF expression. Our data suggest that release of this repression by FXR1P occurs during lipopolysaccharide-induced macrophage activation. Finally, complementation of the knock-out macrophages with recombinant FXR1P resulted in decreased TNF protein production, supporting our findings that FXR1P operates as a repressor of TNF translation.
Garnon
James
J
McGill University Health Centre, McGill University, Department of Experimental Medicine, Montreal, Quebec H3G 1A4, Canada.
Lachance
Claude
C
Di Marco
Sergio
S
Hel
Zdenek
Z
Marion
Dominique
D
Ruiz
Maria C
MC
Newkirk
Marianna M
MM
Khandjian
Edouard W
EW
Radzioch
Danuta
D
D020413:3' Untranslated Regions / Q000235:genetics / Q000378:metabolism; D020856:AT Rich Sequence / Q000235:genetics; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D015536:Down-Regulation; D005600:Fragile X Syndrome; D005786:Gene Expression Regulation / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D014176:Protein Biosynthesis / Q000235:genetics*; D012313:RNA / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
D020413:3' Untranslated Regions; C496283:Fxr1h protein, mouse; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014409:Tumor Necrosis Factor-alpha; D012313:RNA