Identification of calreticulin as a rubella virus RNA binding protein.

AUTOR(ES)

Singh, N K

RESUMO

Previously, we observed that sequences at the 3' end of rubella virus (RV) genomic RNA that form a stable stem-loop structure are necessary for initiation of RNA replication. A cytosolic protein found in Vero 76 cells (simian origin) specifically bound to the 3' (+)-stem-loop 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. A 2-fold increase in phosphorylation of this form of calreticulin is observed in RV-infected cells. Recombinant human calreticulin can bind RV 3' (+)-stem-loop RNA only after undergoing in vitro phosphorylation. This binding activity is abrogated by pretreatment of phosphorylated recombinant human calreticulin with alkaline phosphatase. The RV RNA was also immunoprecipitated from RV-infected UV-crosslinked Vero 76 cells by using calreticulin antibodies. Our results show that phosphorylated calreticulin is an RNA binding protein and phosphorylation is necessary for this activity. Specific binding of calreticulin to the cis-acting element of RV RNA in vivo suggests a possible role for this interaction in viral replication.

Documentos Relacionados

• The rubella virus RNA binding activity of human calreticulin is localized to the N-terminal domain.
• Identification of a novel HIV-1 TAR RNA bulge binding protein.
• Identification of a high-affinity RNA-binding site for the human immunodeficiency virus type 1 Rev protein.
• A double life: cytosolic aconitase as a regulatory RNA binding protein.
• Identification of a promoter region for 3.6-kilobase mRNA of hepatitis B virus and specific cellular binding protein.