Figure 1.

Negative selection screen for infection-resistant cells. A gene-trap library in Blm-deficient embryonic stem (ES) cells was co-cultivated with the irradiated viral producer cell line B4-5 and selected in 1-(-2-deoxy-2-fluoro-1-β-D-arabino-furanosyl)-5-iodouracil (FIAU). Single cell clones surviving the primary negative selection screen were tested twice by exposure to viral supernatant and selection in puromycin to confirm whether they were resistant to infection. The confirmed infection-resistant clones were then molecularly characterized.