Fig. 5. SIN3 binds steroid hormone-regulated loci. (A) A single polytene chromosome spread stained for both SIN3 and SMRTER. (B–D) Higher magnification images of a section of the spread in (A). Spheres indicate loci strongly stained for both SIN3 and SMRTER (yellow); a diamond indicates a locus stained for SIN3 but not SMRTER (green). Co-localization of two antibodies appears as yellow fluorescence. Chromosome arms (X, 2L, 2R, 3L, 3R and 4) are indicated at the tip and the chromocenter is indicated by a C. Antibodies used for staining are indicated at the bottom of each panel. The color of the lettering matches the color of the fluorescence. (E and F) High magnification images of chromosome 4 of spreads stained with SIN3 prepared from flies of a wild-type (E) or an Sgs-4 transgenic (F) line. The transgenic line has a fluorescent signal at the P-element insertion site at 102D3-5 (yellow arrow) in addition to the single strong band present in the wild-type line (red arrow).