Fig. 2.

Comparison of the level of Renilla luciferase expression (A) and viral RNA synthesis (B) by replication-competent (REP) and replication-deficient (NR) SARS-CoV replicons; time-course of RLuc expression by the SARS-CoV replicon (C); the effect of SUD deletion (two clones, clon1 and clon2) on Renilla luciferase expression (D), effect of deletion of the X domain (ΔX), SUD macrodomains (ΔN and ΔM), and of the SUD-C subdomain (ΔC) on the expression of Renilla luciferase (E) and on viral RNA synthesis (F). SARS-CoV replicons with deleted domains were transfected in Vero E6 cells and after 24 h of incubation, Renilla luciferase activity and the amount of viral RNA were measured (see Materials and methods). Renilla luciferase activity and viral RNA synthesis were also measured after transfection of a replication-deficient SARS-CoV replicon (NR) and in mock-transfected cells (Cells). Data shown are from quadruplicate experiments, expressed as the mean value of RNA copies±standard deviation (SD). The difference in expression of the full-length SARS-CoV replicon and its various mutants was found to be significant, implying that values among them are greater than would be expected by chance (0.01>p>0.001). Note that in the replication-deficient SARS-CoV replicon (NR), the sequence of the MluI-MluI fragment is reversed, thus preventing the formation of the replicase complex. RLU – relative light units.