Remote regulatory sequences of the Drosophila glue gene sgs3 as revealed by P-element transformation.

We have examined the transcriptional activity of the Formosa sgs3 glue gene reinserted in the Drosophila genome in transposons containing various arrangements of its natural flanking sequences. The shortest transposons, retaining 127 bp of 5' sequence show no (or very rare) expression. Constructs with up to 1.4 kb of 5' sequence show tissue- and stage-specific accumulation of transcripts, but at severely reduced levels when compared with the resident sgs3 glue gene. To obtain wild-type levels of transcripts, sequences contained in the next 1.3 kb are necessary. At least one regulatory element defined by these experiments is bi-directional. Our results show that marked P-element transformation vectors can be used to analyze regulatory elements of linked genes.