FIG. 1.

Map of PRE region and subfragments. The bxd PRE region is shown with a scale marked in kilobases centered at the EcoRI site which corresponds to position 218241 in the BX-C sequence (24), while the StyI site is at position 219797. The Ubx promoter in this scale would lie at position +24. The positions of the embryonic enhancers S1 and S2 are indicated by boxes below the line. The map also shows the approximate positions of GAGAG sequences (G) and of Zeste binding sites (Z). The subfragments, whose sizes in base pairs are indicated, were prepared using restriction enzymes EcoRI (E), HinfI (Hf), AvaII (Av), BglI (Bg), PstI (P), StyI (St), and KpnI (K).