Fig. 5. Deletion analysis used to map MSL complex-recruiting activity within roX1 transgenes. (A) Diagram of the roX1 fragments tested in transgenic assays. (B–G) Male polytene chromosomes from each transgenic strain were immunostained with anti-MSL1 (red) and counterstained by DAPI (blue). The integration site of each transgene is represented by an arrowhead. Two constructs that share a 300 bp overlap and show strong anti-MSL staining were [roX1a]66B (B) and [roX1.R3′]82CD (C). A 217 bp fragment [roX1-S]48AB (D and E) and a 9× tandem repeat of roX1-S [roX1-SM]57C, F and G) also showed MSL1 localization to the transgene insertion site. Spreading from these small roX1 derivatives is seen in (E) and (G) (arrowheads).