Fig. 9.

Model for two different gene silencing mechanisms. (A) Transgene cassette without Rep-P cannot establish LCR–Rep-P interaction. The transgene is silenced by a DNA methylation-dependent maintenance gene silencing mechanism. (B) Transgene cassette with wild-type Rep-P. The LCR-AG interaction mediated by the LARC complex prevents gene silencing. (C and D) In the Rep-PAG2 cassette, GFP expression is silenced (C), but after about 1 week of zebularine treatment (D), GFP expression is activated upon DNA demethylation. (E) Gene expression is resilenced by the primary/de novo silencing mechanism after prolonged DNA demethylation.