Abstract
The Sgs-4 glue protein gene of Drosophila is expressed only in third-instar larval salivary glands. Previous work suggests that a regulatory region lies 5' and remote to the gene, as indicated by a region of tissue-specific DNase I hypersensitivity and by underproducing mutants with DNA lesions in the hypersensitive region. Here we demonstrate by germ line transformation of cloned fragments containing Sgs-4 that the sequences between 840 bp 5' and 130 bp 3' to the gene are sufficient for Sgs-4 activity. When 5' sequence was removed to -392, activity was eliminated, thereby verifying the existence of essential sequences far upstream. Fragments that are active include, in addition to the capacity for normal levels of expression, three other cis-acting regulatory activities: developmental timing, tissue specificity, and dosage compensation. In contrast, the fragments tested did not specify formation of the puff with which Sgs-4 is normally associated. As shown by chromosomal rearrangements, the region required for puffing is limited to 16-19 kb surrounding the gene.
