Cellular proteins mediate 5′–3′ end contacts of Norwalk virus genomic RNA

Long-range RNA–RNA interactions between the 5′ and 3′ ends are a common feature involved in the regulation of both the initiation of translation and the synthesis of the viral genomic RNAs. These interactions either take place by direct RNA–RNA contacts or can be mediated by proteins. By in silico analysis, we found three possible complementary sequences (CS) between the 5′ and the 3′ ends of the Norwalk virus genomic RNA. Co-precipitation assays demonstrated that physical contacts between the 5′ and the 3′ ends of the NV genomic RNA were stabilized by cellular proteins. Mutations and deletions within these regions, that altered the formation of the CS-1 motif disrupted the 5′–3′ end contacts, while mutations that restore complementarity of the CS-1 motif, recover the ability to form these contacts. These results suggest that the NV genomic 5′–3′ end contacts initially occur by RNA–RNA interactions but are further stabilized by cellular proteins.