FIG. 5.

Full-site integration is correlated to DNase I protection by IN at the LTR termini. (A) The single-end-labeled 3.6-kbp fragment containing “G” sequences on the U3 LTR end was assembled with IN at different concentrations. (B) The rest of the assembly mixtures in A were subjected to DNase I digestion. The DNase I-treated samples were subjected to electrophoresis on a denaturing 8% polyacrylamide gel. Equivalent counts were loaded per lane. The far left lane contains the untreated 3.6-kbp DNA (Neg.). The two adjacent lanes are G/A and C/T chemical reactions. The concentrations of IN in lanes 1 to 7 were 0, 5, 10, 20, 30, 40, and 50 nM, respectively. The nucleotide positions numbered from the blunt-end are marked (right) and the area protected by IN (vertical rectangle) mapping ∼20 bp from the end is shown. Chemical markers have one less nucleotide than the adjacent fragments produced by DNase I. The dried gel was exposed to X-ray film for 10 days without an intensifying screen.