FIG. 4.

Target site selection by RSV integrases. Details and reaction conditions were as described in the legend to Fig. 3, except that the viral DNA substrates were derived from RSV and reactions conducted with Mg²⁺ did not contain DMSO. (A) Processing assay. Reactions were incubated with protein buffer (lanes 1 and 6), wild-type RSV integrase (lanes 2 and 7), or RSV integrases with the indicated amino acid substitutions (lanes 3 to 5 and 8 to 10). (B) Joining assay. Lanes 4 and 10 were loaded with approximately twofold more counts per minute than the other lanes. (C) Insertion assay. Two PCR results are shown for each of the indicated proteins but only from reactions conducted with Mg²⁺; similar results, but different patterns, were obtained in reactions with Mn²⁺. (D) Nonspecific alcoholysis assay. The prominent products created by the wild-type RSV integrase are circled at the left. Bands indicated by the dash or geometric symbols in panels B, C, and D are discussed in the text.