Transgenic construct used to study the Polycomb response element (PRE) from the Ubx upstream control region. Consists of an FRT cassette containing a 1.6kb fragment that encompasses the Ubx PRE, upstream of a reporter gene composed of the 817 bp SspI-MlnI dpp enhancer fragment from Ecol\lacZdpp.SsM in its endogenous orientation, a minimal TATA box from Hsp70, the Hps70 5'UTR and lacZ.