Figure 4. ENY2 is essential for the barrier activity of dCTCF-dependent insulators Fab-8 and Mcp in transgenic lines. (A) The Fab-8 and Mcp insulators are indicated by gray rectangle. In schemes of the constructs (drawn not to scale), the yellow coding region and the white gene (marker) are shown as white rectangles. The yellow coding region is separated by the intron. Arrows indicate the direction of yellow and white transcription. The enhancer controlling yellow expression in bristles is represented by white oval. The 660-bp PRE is indicated by black pentagon. Downward arrows mark the lox and frt sites. In construct names, the corresponding excisable element is parenthesized. Ey is the abbreviation for “enhancers of yellow gene.” The yellow expression in bristles is shown in the selected transgenic lines before and after deletion of either the insulator or PRE in the e(y)2u1 background. The degree of yellow expression in bristles of the thorax and head was scored using a five-point scale: (1) loss of pigmentation, (ev) extreme variegation, (mv) moderate variegation, (wv) weak variegation, and (5) wild-type pigmentation (for details, see the text). The “degree” column shows the numbers of transgenic lines with different bristle pigmentation levels. N is the number of lines in which flies acquired a new yellow phenotype relative to the initial lines. T is the total number of lines examined for each particular construct. (B) The Fab-8 and Mcp insulators with mutated dCTCF binding sites shown as white rectangles.