Previously, we observed that sequences at the
3' end of rubella virus (RV) genomic RNA that form a stable
stem-oop structure are necessary for initiation of RNA replication.
A cytosolic protein found in Vero 76 cells (simian origin)
specifically bound to the 3' (+)-stem4oop sequence. In the
present study, we have purified the RNA binding protein and
identified it as a simian homologue of human calreticulin. The
purified calreticulin binds to the RV RNA with specificity
similar to the protein present in cytosolic extracts. Human
calreticulin antibodies recognize several forms of simian calreticulin,
one of which is phosphorylated in vivo.