The polypyrimidine tract-binding protein (PTB) is involved in the post-transcriptional regulation of human inducible nitric oxide synthase expression.
Human inducible nitric oxide synthase (iNOS) expression is regulated by transcriptional and post-transcriptional mechanisms. We have recently shown that the multifunctional RNA-binding proteins KH-type splicing regulatory protein and tristetraprolin are critically involved in the post-transcriptional regulation of human iNOS expression. Several reports have shown that KH-type splicing regulatory protein colocalizes with the polypyrimidine tract-binding protein (PTB), and both RNA-binding proteins seem to interact with the same mRNAs. Therefore we analyzed the involvement of PTB in human iNOS expression. In human DLD-1 cells, cytokine incubation necessary to induce iNOS expression did not change PTB localization or expression. However, intracellular binding of PTB to the human iNOS mRNA increased after cytokine stimulation. Overexpression of PTB resulted in enhanced cytokine-induced iNOS expression. Accordingly, small interfering RNA-mediated knock down of PTB reduced cytokine-dependent iNOS expression. Recombinant PTB displayed binding to an UC-rich sequence in the 3'-untranslated region of the human iNOS mRNA. Transfection experiments showed that PTB mediates its effect on iNOS expression via binding to this region. The underlying mechanism is based on a modulation of iNOS mRNA stability. In summary, human iNOS is the first example of a human pro-inflammatory gene regulated by PTB on the level of mRNA stability.
Pautz
Andrea
A
Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, D-55101 Mainz, Germany.
Linker
Katrin
K
Hubrich
Thomas
T
Korhonen
Riku
R
Altenhöfer
Sebastian
S
Kleinert
Hartmut
H
D002277:Carcinoma / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000473:pathology; D016207:Cytokines / Q000494:pharmacology; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology; D015971:Gene Expression Regulation, Enzymologic; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D052247:Nitric Oxide Synthase Type II / Q000235:genetics* / Q000378:metabolism*; D038941:Polypyrimidine Tract-Binding Protein / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
D016207:Cytokines; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D038941:Polypyrimidine Tract-Binding Protein; D049452:Green Fluorescent Proteins; D004004:Dichlororibofuranosylbenzimidazole; D052247:Nitric Oxide Synthase Type II