Table 1. Relative retrotransposition rate of the different tagged constructs in HeLa cells under the same transfection conditions.
| Mobile element | Rate G418R colonies (×106/µg at 72 h) mean±SD† | “Relative” rate* | Time requirement for insert (h) |
| L1¥ | 7880.0±321.0 | 5000 | ∼48 |
| Alu (pol III)$ | 1053.3±160.8 | 500 | ∼24 |
| 7SL$ | 66.7±12.6 | 25 | ∼24 |
| U6$ | 67.1±11.3 | 25 | ∼24 |
| hY1$ | 16.7±1.6 | 10 | ∼24 |
| hY3$ | 36.9±7.0 | 20 | ∼24 |
| hY4$ | 57.5±6.4 | 25 | ∼24 |
| hY5$ | 47.5±9.4 | 25 | ∼24 |
| ORF1$ (pol II) | 23.1±5.5 | 10 | ∼48 |
| Alu (pol II)^ | 1.3±0.9 | 1 | ∼48 |
†: Rates were calculated by determining the number of G418 resistant colonies generated at 72 h, per 1 million cells per µg of transfected plasmid. Rates should not be considered as absolute numbers, as results will vary for different cell lines and conditions.
*: Due to the intrinsic experimental variation, a rough approximation was used to determine the relative retrotransposition rates. The lowest observed rate was arbitrarily designated as “1.”
¥: Data from the JM101/L1.3 construct.
Retrotransposition of the element was driven by an optimized L1 ORF2 expression plasmid (pBudORF2opt). Rates were much lower when a full-length wild type L1 was used as the driver for retrotransposition (not shown).
Retrotransposition of the element was driven by cotransfection with L1 ORF1 and ORF2 expression plasmids (pBudORF1opt and pBudORF2opt).