Duarte, R.A.B., Department of Zoology, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa
Stein, L., Department of Zoology, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa
Fabian, B.C., Department of Zoology, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa
Segev, O., Department of Zoology, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa

Chloramphenicol acetyl transferase reporter plasmids driven by the Drosophila ras2/rop promoter were injected into Xenopus oocytes to study Dras2 and rop gene regulation by their bidirectional promoter. When injected without Drosophila nuclear extract, both Dras2 and rop were highly expressed. Dras2 and rop-CAT expression was very similar in Drosophila cells and Xenopus oocytes, suggesting the conservation of regulatory factors between the two species. When Drosophila nuclear extract was co-injected with Dras2 and rop promoter-CAT constructs, expression was inhibited. Inhibition decreased with elevation of plasmid concentration and was increased with an increase in nuclear extract concentration. Since specific DNA-protein interactions were diminished by the combination of oocyte and Drosophila nuclear extracts in gel retardation assays, a sequestering-type mechanism of repression has been proposed.