Table 1 . The insertion distribution of the piggyBac transposon differs significantly from the distribution of TTAA sites relative to defined genomic loci.
| Randomized TTAA sites (%) | piggyBac distribution (%) | SP1-directed distribution (%) | |
|---|---|---|---|
| In RefSeq genes | 38.9 | 44.6 | 45.4 |
| RefSeq UTRs | 6.6 | 9.2 | 12.3 |
| RefSeq introns | 30.9 | 33.1 | 26.1 |
| RefSeq exons | 1.4 | 2.3 | 7.0 |
| First exon | 0.1 | 0.6 | 5.2 |
| First intron | 10.1 | 15.6 | 22.2 |
| ±5 kb transcription start sites | 6.1 | 13.7 | 40.1 |
| ±5 kb from CpG islands | 6.1 | 10.5 | 25.7 |
| ±1 kb from CpG islands | 1.7 | 3.7 | 13.9 |
The distribution of SP1-PBase catalyzed insertions differs from the distribution of insertions catalyzed by the native transposase with large increases in insertions near transcription start sites and CpG islands.