Cell proteins TIA-1 and TIAR interact with the 3' stem-loop of the West Nile virus complementary minus-strand RNA and facilitate virus replication.

It was reported previously that four baby hamster kidney (BHK) proteins with molecular masses of 108, 60, 50, and 42 kDa bind specifically to the 3'-terminal stem-loop of the West Nile virus minus-stand RNA [WNV 3'(-) SL RNA] (P. Y. Shi, W. Li, and M. A. Brinton, J. Virol. 70:6278-6287, 1996). In this study, p42 was purified using an RNA affinity column and identified as TIAR by peptide sequencing. A 42-kDa UV-cross-linked viral RNA-cell protein complex formed in BHK cytoplasmic extracts incubated with the WNV 3'(-) SL RNA was immunoprecipitated by anti-TIAR antibody. Both TIAR and the closely related protein TIA-1 are members of the RNA recognition motif (RRM) family of RNA binding proteins. TIA-1 also binds to the WNV 3'(-) SL RNA. The specificity of these viral RNA-cell protein interactions was demonstrated using recombinant proteins in competition gel mobility shift assays. The binding site for the WNV 3'(-) SL RNA was mapped to RRM2 on both TIAR and TIA-1. However, the dissociation constant (K(d)) for the interaction between TIAR RRM2 and the WNV 3'(-) SL RNA was 1.5 x 10(-8), while that for TIA-1 RRM2 was 1.12 x 10(-7). WNV growth was less efficient in murine TIAR knockout cell lines than in control cells. This effect was not observed for two other types of RNA viruses or two types of DNA viruses. Reconstitution of the TIAR knockout cells with TIAR increased the efficiency of WNV growth, but neither the level of TIAR nor WNV replication was as high as in control cells. These data suggest a functional role for TIAR and possibly also for TIA-1 during WNV replication.