Figure 4.

Proposed models of sfRNA interactions in viral replication and the host response. (A) Potential influences of sfRNA on viral gRNA replication: (i) sfRNA may prevent gRNA cyclisation, inhibiting (–) strand synthesis; (ii) sfRNA may interact via cyclisation sequences to assist in unwinding dsRNA in the replicative form at the (+) strand 5' end, this may promote increased (+) strand synthesis; (iii) sfRNA may competitively bind and sequester translation and/or replication factors, inhibiting translation and replication of gRNA; (B) Different host response pathways inhibited by sfRNA: sfRNA interaction with XRN1 disrupts host mRNA decay; sfRNA suppresses host RNAi pathways likely through interaction with Dicer; sfRNA inhibits the IFN-α/β response via an unknown mechanism. Each of these pathways cross-communicates and may influence the activities of the others.