Transgenic construct used to study a Polycomb Group response element (PRE) from the en locus. Generated using the pP{CaSpeR} vector; the 'PRE1.1X' en fragment (the distal end of this fragment is -1944bp relative to the en transcription start site and the proximal end is between -1671 and -1503bp) has been inserted upstream of the w+mC minigene.