RESUMO
Members of the picornavirus family initiate translation of their RNA genomes by a cap-independent mechanism in which ribosomes bind to an internal site in the 5' untranslated region (5'-UTR). This unique process requires an internal ribosome entry site (IRES), a highly structured RNA whose function is mediated in part by interactions with cell proteins. The IRES element of human rhinovirus 2 (HRV-2) extends from nucleotide (nt) 10 to between nt 544 and 568 and has been shown to interact with two cell proteins, pyrimidine tract-binding protein (pPTB) and p97. To map the specific regions of HRV-14 RNA that bind cell proteins, mobility shift, UV cross-linking and Western immunoblot analyses were performed. The results indicate that an RNA sequence from nt 538 to 591 interacts with pPTB and La, two proteins previously shown to functionally interact with the IRES elements of several picornaviruses. Two additional proteins, p97 and p68, were also cross-linked to nt 538 to 591 RNA. These four proteins interact with a putatively unstructured portion of the 5'-UTR that contains a polypyrimidine tract and has been shown to be present at the 3' border of sequences that are essential for IRES function of HRV-2. These protein-RNA interactions are likely to play a role in internal initiation of translation.