Other Drosophila insulators block <i>eve</i> PRE action, and other PREs are blocked by Homie.

<p><b>A:</b> fluorescence from transgenic <i>TER94-GFP</i> in the context of the transgene diagrammed in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003883#pgen-1003883-g001" target="_blank">Figure 1A</a> at the 95E5 landing site, with Homie replaced by either λ phage DNA (“ΔHomie”) or the indicated insulator. Diagrams below each panel show the arrangement of regulatory elements affecting GFP expression: yellow-filled boxes are PREs, either from <i>eve</i> (unlabeled), <i>en</i>, or the <i>bxd</i> region of <i>Ubx</i>, as indicated; red-filled boxes are insulators, either Homie (unlabeled), or as labeled. Note that each of these insulators restore <i>TER94</i> promoter activity, although <i>scs</i> does so when inserted in one orientation (“<i>scs</i>(inv)”) but not the other (“<i>scs</i>”) relative to the <i>TER94-GFP</i> promoter. Note also that restoration of GFP expression is somewhat weaker for <i>scs'</i> and <i>scs</i> (even in the “inverted” orientation) than for <i>gypsy</i> and <i>Fab-7</i>, indicating that they only partially block <i>eve</i> PRE action. <b>B:</b> same as in A, except that the transgenes were inserted in opposite orientation at the same landing site relative to that in A, with either the <i>gypsy</i> insulator or the <i>Fab-8</i> insulator. Note that <i>eve</i> PRE action is blocked in both cases, causing strong fluorescence. <b>C:</b> fluorescence from transgenic <i>TER94-GFP</i> in the context of the transgene diagrammed in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003883#pgen-1003883-g001" target="_blank">Figure 1A</a>, with Homie deleted, and with either the <i>eve</i> PRE deleted (“ΔHomie ΔPRE”), or replaced by the <i>bxd</i> PRE (“+ <i>bxd</i> PRE”) or the <i>en</i> PRE (“+ <i>en</i> PRE”). Note that each of these PREs repress <i>TER94-GFP</i> to a similar degree as does the <i>eve</i> PRE in the absence of an insulator (compare to “ΔHomie” panels in A and B, where the <i>eve</i> PRE is present). <b>D:</b> fluorescence from transgenic <i>TER94-GFP</i> in the context of the transgene diagrammed in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003883#pgen-1003883-g001" target="_blank">Figure 1A</a>, with the <i>eve</i> PRE either removed (“ΔPRE”), or replaced by either the <i>bxd</i> PRE (“+ <i>bxd</i> PRE”) or the <i>en</i> PRE (“+ <i>en</i> PRE”). Note that neither of these PREs is able to repress <i>TER94-GFP</i> when Homie is present, showing that Homie blocks the repressive action of these heterologous PREs.