Figure 4.

Retroviral infection resistant mutants. (a) Retroviral gene-trap mutagenesis. Illustration of the retroviral producer construct, RGTV-1, with the SAβgeo gene trap cassette in the retroviral vector backbone, an integrated provirus in the intron of a gene, and a Cre-reverted allele with a single long terminal repeat (LTR) retained in the locus. βgeo, lacZ-neo fusion gene; SA, splice acceptor. (b) Retroviral infection resistant phenotype of five independent mutant clones. Daughter embryonic stem (ES) cell clones from five different pools and controls were plated in triplicate in 24-well plates. 'No drug' indicates that all clones grew without selection; 'Puromycin selection' indicates that all clones were puromycin sensitive; and 'Viral infection + Puromycin selection' indicates that all clones were exposed to 1.2 × 10⁵ colony-forming units of the B4-5 puro-Δtk retroviral vector followed by selection. The NGG5.3 controls were readily infected and clones from pools 1 and 7 were highly resistant to infection; clones from pools 2, 3, and 4 were less resistant to infection.