The positive and negative transcriptional regulation of the Drosophila Gapdh-2 gene.

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Abstract
One of the genes encoding glyceraldehyde 3-phosphate dehydrogenase of Drosophila melanogaster, Gapdh-2, is expressed in all cell types examined, but its level of expression is regulated developmentally. Here we report the analysis of the regulatory sequences for the transcription of Gapdh-2. We have generated Gapdh-2-LacZ fusion genes in which the 5'-flanking sequence of Gapdh-2 has been mutated. Examination of the expression of these fusion genes, which have been introduced by transfection into the Schneider II cell line and by germ-line transformation into flies, led to the identification of two distinct regulatory regions, URS-1 and URS-2, within the first 145 bp of the 5'-flanking sequence of Gapdh-2. URS-1 activates transcription throughout the development of Drosophila. However, URS-2 exhibits a dual function during the development. It clearly represses transcription in Schneider II cells, and perhaps also in mid-stage embryos. In contrast, it activates transcription in larvae and adult flies. Thus, URS-2 plays a key role in the developmental regulation of Gapdh-2. Additionally, the efficient transcription of Gapdh-2 in larval and adult stages appears to depend on a synergistic function of URS-1 and URS-2.