The Drosophila Eve gene has a complex promoter containing mu

The Drosophila Eve gene has a complex promoter containing multiple binding; sites for four transcription regulators: Bicoid, Hunchback. Giant, and Kruppel repress of Eve transcription, whereas Giant and Kruppel repress Eve transcription. Figure Q8-66A shows patterns of expression of these regulators. The Eve promoter contains modules that control expression in various stripes. You construct a reporter gene that contains the DNA 5 kb upstream of the Eve gene, so that this reporter contains the stripe 3 module, the stripe 2 module, the stripe 7 module, and the TATA box, all fused to the LacZ reporter gene (which encodes the 3-galactosidase enzyme), as shown in Figure Q8-66B. This construct results in expression of the p-galactosidase enzyme in three stripes, which correspond to the normal positions of stripes 3, 2, and 7. A. By examining the overlap of sites on the stripe 2 module, as depicted in Figure Q8-66B, what is the biological effect of having some of the transcription regulator binding sites overlap? B. You make two mutant versions in which several of the binding sites in the Eve stripe 2 module have been deleted, as detailed in items (i) and (ii) below. Refer to Figure Q8-66B for the positions of the binding sites. (Note, however, that because many of the binding sites overlap, it is not possible to delete all of one kind of site without affecting some of the other sites.) Match the appropriate mutant condition with the most likely pattern of Eve expression shown in Figure Q8-66C. Explain your choices. i) deletion of the Kruppel-binding sites in stripe 2 module that are marked with an asterisk (*) in Figure Q8-66B.

Solution

A. transcriptional regulator binding site leads to gene product lost

B. i) Kruppel is the reporter of eve stripe 2, deletion of kruppel binding sites should cause a broadening of the eve stripe 2 expression domain, and this shift should be to be posterior since kruppel is normally expressed just posterior to the position of eve stripe 2, in a wild-type embryo

ii) Bicoid protein act as transcriptional activator