GAGA factor down-regulates its own promoter.

GAGA factor is involved in many nuclear transactions, notably in transcription as an activator in Drosophila. The genomic region corresponding to the Trl promoter has been obtained, and a minimal version of a fully active Trl promoter has been defined using transient transfection assays in S2 cells. DNase I footprinting analysis has shown that this region contains multiple GAGA binding sites, suggesting a potential regulatory role of GAGA on its own promoter. The study shows that GAGA down-regulates Trl expression. The repression does not depend on the GAGA isoform, but binding to DNA is absolutely required. A fragment of the Trl promoter can mediate repression to a heterologous promoter only upon GAGA overexpression in transiently transfected S2 cells. Chromatin immunoprecipitation analysis of S2 cells confirmed that GAGA factors are bound to the Trl promoter over a region of 1.4 kbp. Using a double-stranded RNA interference approach, we show that endogenous GAGA factors limit Trl expression in S2 cells. Our results open the possibility of observing similar GAGA repressive effects on other promoters.