FIG. 4.

Strategy for PCR amplification of proviral LTRs and DNA sequencing. All abbreviations are the same as in Fig. 1. Zigzag lines, host DNA sequences; large arrows, PCR primers; small horizontal arrows, sequencing primers. Because the primers were located in U3 and in Ψ⁺, only sequences from the upstream LTR and a small portion of the Ψ⁺ were amplified.