Transgenic construct used to study Polycomb response element (PRE) activity. Generated in vivo by integration of donor plasmid sequence into the attP site present in the P{w3'.y+.attP} element. As a result of the integration event, en PRE1 sequence (coordinates 2R:11529390..11529821 , release 6 genome) in which the Trl protein-binding sites have been mutated, is inserted directly upstream of a reconstituted w[+] reporter.