The Drosophila eve Insulator Homie Promotes eve Expression and Protects the Adjacent Gene from Repression by Polycomb Spreading
Figure 2
Homie blocks PRE action in ovaries.
Fluorescence and GFP RNA levels in ovarioles from fly lines carrying the indicated transgenic reporters (described in Figure 1), or no transgene (“no t'gene”). Note the strong fluorescence from TER94 promoter-driven GFP with the intact transgene (“intact t'gene”) at all stages of oogenesis (which proceeds from left to right within each string of ovarioles), and that this is lost when Homie is deleted (“ΔHomie”). Remarkably, strong GFP expression is restored when both Homie and the PRE are deleted (“ΔHomie ΔPRE”), indicating that in the absence of Homie, the PRE is responsible for repression of TER94-GFP. Strong expression is also seen when only the PRE is removed (“ΔPRE”). The graph at the bottom shows, on a log scale, the results of quantitation in triplicate (averages with standard deviations) of GFP RNA from ovaries of lines carrying the indicated transgenes (see Materials and Methods). Note that GFP RNA levels decrease more than 50-fold when Homie is deleted, and are restored by additional deletion of the PRE.