High impact information on Sgs3

• 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 [1].
• Thus the normal product of the l(1)npr-1 gene is required for regression of the 68C puff, and the l(1)npr-1 gene product allows expression of the Sgs-3 gene by interacting, either directly or indirectly, with DNA sequences near this glue protein gene [2].
• The 68C locus in the polytene chromosomes of Drosophila melanogaster salivary glands is puffed during the last half of the third larval instar and harbors the structural gene for sgs3, one of the glue polypeptides synthesized by the glands during this period [3].
• The Drosophila salivary gland secretion protein gene, Sgs3, has a consensus TATA sequence and gives rise to abundant stage and tissue-specific transcripts [4].
• Drosophila Sgs3 TATA: effects of point mutations on expression in vivo and protein binding in vitro with staged nuclear extracts [4].

Biological context of Sgs3

• Here we show that the fork head encoded protein binds to an upstream regulatory region of the larval salivary gland glue protein gene Sgs3 [5].
• The 68C region of the Drosophila melanogaster salivary gland polytene chromosomes harbors the structural genes for the three salivary gland glue proteins sgs-3, sgs-7, and sgs-8 [6].
• Although important for the overall levels of Sgs-3 expression, they are clearly not strong, viral-like enhancer elements [7].
• Using P element-mediated transformation, we have introduced defined segments of the 68C region into the fly genome and assayed the expression of the Sgs-3 gene [8].
• The data are consistent with the hypothesis that the ecdysone receptor directly contributes to the transcriptional activation of Sgs-3 by binding to at least one of the two elements [9].

Associations of Sgs3 with chemical compounds

• This transition is prevented in Drosophila larvae mutated in the ecdysone-dependent 2B5 locus, in which Sgs3 is inactive and GEBF-I, a Glue Enhancer Binding Factor, is missing [10].

Physical interactions of Sgs3

• Mobility shift assay in the presence of an anti-Fork head antibody demonstrated that the Fork head factor interacts with the TGTTTGC box shown to be involved in tissue-specific Sgs3 expression [5].
• We identified two regulatory elements in the upstream region of the Drosophila Sgs-3 gene which are both able to bind the ecdysone receptor (EcR/USP) and the product of the fork head gene [9].

Other interactions of Sgs3

• In all of the experiments, the RNA products of the Sgs-3, Sgs-7, and Sgs-8 genes acted coordinately [6].
• FKH and SEBP3 have been shown previously to be involved in the regulation of Sgs-3 and Sgs-4 [11].
• Two new regulatory elements controlling the Drosophila Sgs-3 gene are potential ecdysone receptor and fork head binding sites [9].
• It was further shown that each of these proteins is a part of the secreted salivary gland glue: the group IV RNA codes for the previously described sgs-3, whereas the group II and III RNAs code for the newly identified glue polypeptides sgs-8 and sgs-7 [12].
• We have undertaken chromatin studies on transformed Drosophila strains carrying DNA sequences modified in the region of the DNase I (EC 3.1.4.5)-hypersensitive sites -750 and -600 base pairs upstream from the Sgs3 start site [13].

References