TABLE 3.
TK activity in TK(−) cells
| Plasmid | HAT-resistant coloniesa |
|---|---|
| Vector | 0 |
| pCMV-HHV8 ORF 21 | 0 |
| pSV40-HHV8 ORF 21 | 0 |
| pHSV-HHV8 ORF 21 | 0 |
| pHSVTK | >180 |
| pEBVTK | >100 |
a
Data are the number of colonies per 100-mm dish for transfections performed in 143B TK(−) human osteosarcoma cells and mouse LTK(−) fibroblast cells. HHV8 ORF 21 was expressed and tested for TK activity with three different promoters, including CMV, SV40, and HSV TK natural promoters. Results are representative of at least five experiments.