We demonstrate that passing-through transcription suppresses the activity of the white gene enhancer integrated into the intron. At the same time, the SV40 transcription terminators flanking the transgene can completely remove the inhibitory effect of transcription.

We tested the activity of the PRE element from the Drosophila virilis genome, which is the homologue of the known Drosophila melanogaster bxdPRE element from the regulatory region of the Ubx gene. It is easy to select unique primers to this element that do not occur in the Drosophila melanogaster genome. We showed that the studied PRE element causes a strong repression of the white marker gene upon insertion into the Drosophila melanogaster genome and interacts with the PcG proteins of the PRC1 and PhoRC complexes.