LAP (for La peptide) corresponds to amino acids 11 to 28 from the N-terminal €La motif€ of La, a 52-kDa autoantigen found in patients with systemic lupus erythematosus, and one of the first cellular proteins identified to interact with viral internal ribosome entry site (IRES) elements and stimulate poliovirus (PV) and hepatitis C virus (HCV) IRES-mediated translation. LAP efficiently inhibits viral IRES-mediated translation in vitro. LAP does not bind RNA directly but blocks La binding to IRNA and PV 5-UTR.