Y-box protein-1 controls transforming growth factor-beta1 translation in proximal tubular cells.
Transforming growth factor-beta1 (TGF-beta1) mRNA has low basal translational efficiency in proximal tubule cells; however, its translation is stimulated by profibrotic cytokines. We studied the role of the multifunctional Y-box protein-1 (YB-1) in regulating proximal tubule cell TGF-beta1 translation. Using RNA-electrophoretic mobility shift assays and ultraviolet crosslinking, we found two protein complexes of 50 and 100 kDa, which bound to the TGF-beta1 mRNA 5'-untranslated region. Supershift studies using antibodies to YB-1 showed that both sites contained YB-1 as did studies with recombinant YB-1, which demonstrated that it was sufficient to form both complexes. RNA competition experiments confirmed YB-1 binding to the two predicted binding sites; one with high affinity and the other with lower affinity. Strong basal YB-1 association with TGF-beta1 mRNA was found in proximal tubule cells, which decreased when platelet-derived growth factor was used to activate TGF-beta1 translation. In contrast, knockdown of proximal tubule cell YB-1 expression abrogated TGF-beta1 synthesis. Our results suggest that TGF-beta1 translation in proximal tubule cells requires YB-1 binding to a high-affinity site in the 5'-untranslated region of its mRNA; however, binding to a low-affinity site inhibits basal translation.
Fraser
D J
DJ
Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, UK.
Phillips
A O
AO
Zhang
X
X
van Roeyen
C R
CR
Muehlenberg
P
P
En-Nia
A
A
Mertens
P R
PR
D020121:5' Untranslated Regions / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*; D051840:Y-Box-Binding Protein 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*
D020121:5' Untranslated Regions; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D053773:Transforming Growth Factor beta1; D051840:Y-Box-Binding Protein 1