FIG. 3.

2-LTR circle junctions derived from infecting cells with PPT mutants. The pbs is indicated by a white box, the leader sequence downstream of the pbs is shown with gray dots, the PPT is a box with black horizontal bars, the U-tract is a gray box, and the sequences immediately upstream of the U-tract are indicated by the box with diagonal bars. This linear viral DNA can be ligated by cellular enzymes in the nucleus of an infected cell to form a 2-LTR circle. A consensus circle junction is shown at the top. Different categories of aberrant 2-LTR circle junctions are shown. Three independent experiments were performed with PPT mutant A box 1-1 to demonstrate the reproducibility of the assay. The results obtained from one experiment are shown for mutants A box 1-5, A box 1-6, and multi-A box.