Construction and applications of exon-trapping gene-targeting vectors with a novel strategy for negative selection

Table 1 Exon-trap-based HPRT-gene targeting in HT1080 cells

Experiment	Number of cells transfected	Total number of puromycin-resistant colonies	Gene-targeting efficiency
1	4.0 × 10⁷	411	0.8% (2/244)
2	4.0 × 10⁷	614	0.4% (2/501)

The targeting vector pHPRT-SH 2A-EGFP-2A-Puro was I-SceI linearized and transfected into HT1080 cells, and the gene-targeting efficiency was determined as described in “Methods”.