FIG. 4.

Selection of substrates for HIV-1 integrase. Multiple rounds of selection by integration, amplification, and regeneration were carried out using HIV-1 integrase and the substrates with the terminal 5 nucleotides randomized (HVP5N) (A) or the 7 nucleotides adjacent to the conserved CA randomized (HVP7NCA) (B). A sample of the reaction mixture of each round was sequenced, and lanes corresponding to termination reaction mixtures are shown. Round 0 is the sequence of the starting pool of double-stranded oligonucleotide substrates without any selection. The starting sequence is shown on the left of the gel, while specific nucleotide sequences emerging in the final round are shown on the right of the gel. The final round is determined by a stronger-than-WT integration efficiency, judging by the intensity of the integration-PCR product.