English: Model of the replicase-transcriptase complex of a coronavirus. Illustration shows how the RNA sliding clamp for processivity and primase domain for priming (nsp7 and nsp8 – green/orange) could assemble on viral dsRNA and interact with the putative multi-subunit coronavirus polymerase complex consisting of RdRp for replication (nsp12 – red), ExoN for proofreading (nsp14 – dark blue), and ExoN cofactor (nsp10 – yellow). To initiate replication-transcription there is a short (∼6 n.t.) primer generated by the non-canonical RdRp activity of nsp8 (I and II). Binding of ssRNA by RNA binding proteins (nsp9 – light blue) to avoid secondary structure is also shown. A helicase to unwind RNA (nsp13) is not shown downstream.