FIG. 6.

Model for error-prone gap repair at proviral integration. The figure illustrates the introduction of mutations at either virus-chromosome junction. (A) Schematic representation of the SL3-3 proviral DNA copy of the genome. The 3′-LTR and 5′-LTR att sites are shown. (B) The integration step is initiated by 3′ processing of two T nucleotides. (C) During strand transfer, the two DNA ends are joined in concert to the chromosomal target DNA 4 bp apart. The target sequence VTAB (V denotes A, C, or G; B denotes C, G, or T) is shown, and the T nucleotide located at the second position is underlined. Due to base pairing, the 5′ dinucleotide overhangs are not removed during the gap repair process. (D) Subsequent editing of the mismatching base pairs (marked with an asterisk) generates the V-to-T mutation at either junction. The figure illustrates the introduction of mutations at both junctions for the same proviral integration; however, it is noted that this is never observed in our data set.