Mapping the minimal MHV-68 oriLyt. The 5′ deletion plasmids pMOΔ6 to -Δ12, pMOΔ2, and pMOΔ5 (A) or 3′ deletion plasmids pMOΔ13 to -Δ16 and pMOΔ3 (B) were tested in replication assays. DNA was extracted from each sample, digested, and analyzed by Southern blotting with radiolabeled pKS as a probe. Lower bracket, DpnI-sensitive input DNA. Upper bracket, DpnI-resistant replicated DNA.