We have analyzed the function of cis-acting elements of rubella virus RNA and the components which interact with these elements in viral RNA replication. We demonstrated that the 5'- and 3'-terminal sequences from RV RNA promote translation and negative-strand RNA synthesis of chimeric chloroamphenicol acetyltransferase (CAT) RNAs. These sequences have a potential to form stem-loop (SL) structures and bind cellular proteins specifically in RNA gel-shift and UV cross-linking assays. The 5' end binding proteins were identified to be Ro/SSA-associated antigens by virtue of being recognized in an RNA complex by an autoimmune patient serum with Ro antigen type specificity. Purification and sequence analysis of the 3' end binding protein revealed that it is a homologue of human calreticulin. The role of host protein in RV replication is discussed.