The RNA-binding protein PTB exerts translational control on 3′-untranslated region of the mRNA for the ATP synthase β-subunit

We have recently reported that RNA-binding proteins TIA-1 (T-cell intracellular antigen-1), TIAR (TIA-1 related protein), and HuR (Hu antigen R) modulate the expression of the ATP synthase β-subunit mRNA (β-F1-ATPase mRNA) [J.M. Izquierdo, Control of the ATP synthase β subunit expression by RNA-binding proteins TIA-1, TIAR, and HuR, Biochem. Biophys. Res. Commun. 348 (2006) 703–711]. Here we found that PTB (Polypyrimidine Tract–Binding Protein) is a novel member of the ribonucleoprotein complex that interacts with the β-F1-ATPase mRNA through an adenosine/uridine (AU)-rich element located to the β-F1-ATPase 3′-untranslated region (β-3′-UTR). Co-expression of GFP from a reporter mRNA quimera containing human β-3′-UTR and recombinant PTB in HeLa cells increased the amount of GFP protein. Interestingly, this effect is not due to increased steady-state levels of GFP-β-3′-UTR mRNA. Taken together, these results suggest that PTB regulates post-transcriptional expression of the β-F1-ATPase mRNA at the translational level.