Specific trans-acting proteins interact with auxiliary RNA polyadenylation elements in the COX-2 3'-UTR.

Two cyclooxygenase (COX) enzymes, COX-1 and COX-2, are present in human cells. While COX-1 is constitutively expressed, COX-2 is inducible and up-regulated in response to many signals. Since increased transcriptional activity accounts for only part of COX-2 up-regulation, we chose to explore other RNA processing mechanisms in the regulation of ...
this gene. Previously, we showed that COX-2 is regulated by alternative polyadenylation, and that the COX-2 proximal polyadenylation signal contains auxiliary upstream sequence elements (USEs) that are very important in efficient polyadenylation. To explore trans-acting protein factors interacting with these cis-acting RNA elements, we performed pull-down assays with HeLa nuclear extract and biotinylated RNA oligonucleotides representing COX-2 USEs. We identified PSF, p54(nrb), PTB, and U1A as proteins specifically bound to the COX-2 USEs. We further explored their participation in polyadenylation using MS2 phage coat protein-MS2 RNA binding site tethering assays, and found that tethering any of these four proteins to the COX-2 USE mutant RNA can compensate for these cis-acting elements. Finally, we suggest that these proteins (p54(nrb), PTB, PSF, and U1A) may interact as a complex since immunoprecipitations of the transfected MS2 fusion proteins coprecipitate the other proteins.
Mesh Terms:
3' Untranslated Regions, Cyclooxygenase 2, Gene Deletion, HeLa Cells, Humans, Membrane Proteins, Models, Biological, Nuclear Matrix-Associated Proteins, Octamer Transcription Factors, Polyadenylation, Polypyrimidine Tract-Binding Protein, Protein Binding, RNA 3' Polyadenylation Signals, RNA, Messenger, RNA-Binding Proteins, Ribonucleoprotein, U1 Small Nuclear, Substrate Specificity
RNA
Date: Jul. 01, 2007
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