Hsp90 interacts specifically with viral RNA and differentially regulates replication initiation of Bamboo mosaic virus and associated satellite RNA

Host factors play crucial roles in the replication of plus-strand rna viruses. in this report,a heat shock protein 90 homologue of nicotiana benthamiana,nbhsp90,was identified in association with partially purified replicase complexes from bamv-infected tissue,and shown to specifically interact with the 3′ untranslated region (3′ utr) of bamv genomic rna,but not with the 3′ utr of bamv-associated satellite rna (satbamv rna) or that of genomic rna of other viruses,such as potato virus x (pvx) or cucumber mosaic virus (cmv). mutational analyses revealed that the interaction occurs between the middle domain of nbhsp90 and domain e of the bamv 3′ utr. the knockdown or inhibition of nbhsp90 suppressed bamv infectivity,but not that of satbamv rna,pvx,or cmv in n. benthamiana. time-course analysis further revealed that the inhibitory effect of 17-aag is significant only during the immediate early stages of bamv replication. moreover,yeast two-hybrid and gst pull-down assays demonstrated the existence of an interaction between nbhsp90 and the bamv rna-dependent rna polymerase. these results reveal a novel role for nbhsp90 in the selective enhancement of bamv replication,most likely through direct interaction with the 3′ utr of bamv rna during the initiation of bamv rna replication. © 2012 huang et al.