Figure 2.

Replaceable 3′ gene entrapment cassettes. (A,B) neomycin- and (C,D) zeocin-resistance genes ending at a 3′-splice site (SD) and RNA destabilization sequence (flash symbol) were cloned downstream of the (A) RNA polymerase II (Pol II) or (B,C,D) phosphoglycerol kinase (PGK) promoters. IntZeoPTC contains a synthetic intron inserted within the Zeocin-resistance gene (D). After gene entrapment, vector sequences splice to downstream exons of cellular genes (black boxes). The sizes of 5′-exons containing Neo and Zeo sequences is indicated in base pairs (bp). Heterospecific loxP sites (loxP and lox5171) allow vector sequences to be replaced by Cre-mediated cassette exchange.