Abstract
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.
