HP1 binding maps. A) Dam-HP1 fusion protein is expressed at very low levels. Western blot is shown of fly head protein extracts of w1118controls (-) or a transgenic line expressing the Dam-HP1 fusion protein from the uninduced hsp70 core promoter (+), probed with an anti-HP1 antibody . Position of HP1 and expected position of (non-detectable) Dam-HP1 fusion protein are marked by arrowheads. B) Cartoon showing the wild-type chr X and the inverted X chromosomes (wm4eand wm51b) used in this study. Inversion breakpoints are indicated with dashed lines. w = white, rst = roughest. Arrow heads (>) indicate the direction on the wild-type chr X. Black-underlined regions are represented on our microarray. Pictures on the right of each chromosome show eye color of representative males. C-D) Chromosomal maps of HP1 binding to ~200 kb regions of chr 2R (C) and chr 4 (D). Grey sticks show wild-type Dam-HP1/Dam binding ratio. Orange and red lines indicate Dam-HP1/Dam binding ratio in wm4eand wm51b, respectively. A running median filter (window size 5) was applied to suppress noise. Genes are plotted as white rectangles. Transposable elements (TEs) are plotted below the genes as grey rectangles. E) Chromosomal map of HP1 binding to the wild-type (Oregon-R-S) chr X for the ~400 kb region surrounding the white gene. Black horizontal line indicates the average Dam-HP1/Dam binding ratio on the first 3.2 Mb of chr X. TE and mini-white sequences possibly cross-hybridize on the microarray and are therefore masked in the plots (indicated with black, uninterrupted thick lines). white is depicted as a red rectangle, crm = cramped, Syx4 = Syntaxin 4. Other features are the same as in C-D. F-G) Chromosomal map of HP1 binding to wm4e(F), and wm51b(G). Vertical dashed line indicates euchromatic inversion breakpoint. In reality the sequence on the right of the break is attached to the pericentric heterochromatin. H) Close-up of the ~90 kb surrounding the white gene (red rectangle). mini-white sequences (hatched rectangles), which are present in the DamID expression vector, possibly cross-hybridize to the endogenous white sequence and are therefore masked. Colors as in E-G.