Regulatory elements and interactions in the Drosophila 68C glue gene cluster.

We reviewed studies on the developmental regulation of the 68C glue gene cluster of Drosophila melanogaster. Extensive transformation analyses of Sgs-3 have shown that four regions necessary for normal expression can be distinguished. The first(+10 to -50) contains the transcription start site and TATA motif. This region can be replaced functionally by corresponding sequences from the hsp70 gene, but it is sensitive to point mutations in the TATA sequence. The second region (-50 to -98) contains more than one upstream sequence that, in combination with the other elements, leads to stage and tissue-specific expression. The third region (centered at -600) contains an element that enhances transcript levels some 20-fold. The final region (between -1.65 and -2.35 kb) contains elements having modest (twofold to threefold) effects on expression, one of which is contained in the coding sequences of Sgs-7, a second member of the cluster.