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 beta-subunit mRNA (beta-F1-ATPase mRNA) [J.M. Izquierdo, Control of the ATP synthase P 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 beta-F1-ATPase mRNA through an adenosine/uridine (AU)-rich element located to the beta-F1-ATPase 3'-untranslated region (beta-3'-UTR). Co-expression of GFP from a reporter mRNA quimera containing human beta-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-beta-3'-UTR mRNA. Taken together, these results suggest that PTB regulates post-transcriptional expression of the beta-F1-ATPase mRNA at the translational level. (c) 2007 Elsevier Inc. All rights reserved.