title: TRIB1 Is Regulated Post-Transcriptionally by Proteasomal and Non-Proteasomal Pathways.
abstract: The TRIB1 gene has been associated with multiple malignancies, plasma triglycerides and coronary artery disease (CAD). Despite the clinical significance of this pseudo-kinase, there is little information on the regulation of TRIB1. Previous studies reported TRIB1 mRNA to be unstable, hinting that TRIB1 might be subject to post-transcriptional regulation. This work explores TRIB1 regulation, focusing on its post-transcriptional aspects. In 3 distinct model systems (HEK293T, HeLa and arterial smooth muscle cells) TRIB1 was undetectable as assessed by western blot. Using recombinant TRIB1 as a proxy, we demonstrate TRIB1 to be highly unstable at the protein and RNA levels. By contrast, recombinant TRIB1 was stable in cellular extracts. Blocking proteasome function led to increased protein steady state levels but failed to rescue protein instability, demonstrating that the 2 processes are uncoupled. Unlike as shown for TRIB2, CUL1 and TRCPβ did not play a role in mediating TRIB1 instability although TRCPβ suppression increased TRIB1 expression. Lastly, we demonstrate that protein instability is independent of TRIB1 subcellular localization. Following the identification of TRIB1 nuclear localization signal, a cytosolic form was engineered. Despite being confined to the cytosol, TRIB1 remained unstable, suggesting that instability occurs at a stage that precedes its nuclear translocation and downstream nuclear function. These results uncover possible avenues of intervention to regulate TRIB1 function by identifying two distinct regulatory axes that control TRIB1 at the post-transcriptional level.
authors.affiliation: Atherogenomics Laboratory, University of Ottawa Heart Institute, Ottawa, Canada.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Soubeyrand
authors.affiliation: Atherogenomics Laboratory, University of Ottawa Heart Institute, Ottawa, Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Martinuk
authors.affiliation: Atherogenomics Laboratory, University of Ottawa Heart Institute, Ottawa, Canada.
authors.forename: Paulina
authors.initials: P
authors.lastname: Lau
authors.affiliation: Atherogenomics Laboratory, University of Ottawa Heart Institute, Ottawa, Canada.|Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Canada.
authors.forename: Ruth
authors.initials: R
authors.lastname: McPherson
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D044842:Cullin Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability / Q000187:drug effects; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D020506:Untranslated Regions; D044844:beta-Transducin Repeat-Containing Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: C100318:Cullin 1; D044842:Cullin Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007976:Leupeptins; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; C493170:TRIB1 protein, human; D020506:Untranslated Regions; D044844:beta-Transducin Repeat-Containing Proteins; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde