Figure 3.

Adaptation to HHPV-2 infection under different cas genetic backgrounds. (A) Cas requirement for adaptation. For each cas mutant, DNA was sampled from cells transformed with an empty plasmid (−) or the plasmid carrying the deleted cas gene(s) (+). The plasmid-carried cas gene(s) was/were under the control of the cas operon promoter. (B) Requirements for the nuclease and helicase activities of Cas3. Alanine replacement was performed for the putative key residues in the HD nuclease domain (H20A, H55A, D56A and D229A) and the DExD/H helicase domain (K315A, D439A and E440A). Another two conserved residues (His6 and Lys113) were also mutated. The empty plasmid (−) and the plasmid carrying a wild-type Cas3 (Cas3^WT) were used, respectively, as negative and positive controls. Lane Ms, dsDNA size markers.