FIG. 2.

ICP8 stimulates UL12 digestion of dsDNA in the presence or absence of strand exchange. (A) The strand exchange assay was performed, and products were separated by agarose gel electrophoresis. All reactions included the ³²P-labeled 1.5-kb dsDNA substrate (20 ng). M13wins ssDNA (100 ng), M13mp18 ssDNA (100 ng), ICP8 (1.75 μM), and UL12 (13.9 nM) were added as indicated. Reaction conditions were as described for Fig. 1. Incubations were for 20 min at 37°C. The phosphorimage of the dried gel is shown. The positions of the double-stranded 1.5-kb substrate (ds) and the strand exchange products (se) are indicated. (B) Samples from the strand exchange reaction shown in panel A were removed at different time points for measurement of nuclease activity. All reactions included the 1.5-kb double-stranded ³²P-labeled substrate. Numbers at the ends of the data curves refer to the lane numbers in panel A. Closed circles, UL12; open squares, UL12 + ICP8; filled squares, UL12 + ICP8 + ssM13wins; closed triangles, UL12 + ICP8 + ssM13mp18; open diamonds, UL12 + ssM13wins; open circles, UL12 + ssM13mp18; open triangles, ICP8.