Figure 4.

Mapping of the region in CP190 required to organize interbands in a polytene chromosome model. (A) Targeting the GAL4 DNA-binding region fused with the myc epitope (DBD) and the 1–1096 aa CP190 regions fused with the GAL4 DNA-binding region and the myc epitope (DBD:CP190 1–1096) to the 16 GAL4 binding sites in the 10A1-2 disc. The left panel demonstrates the polytene chromosomes in phase contrast. The right panel is an overlay of phase contrast and immunostaining with antibodies against myc (red), Chriz (green), Z4 (green), and CP190 (red). Black and white square brackets and white arrows indicate the model 10A1-2 bands in different polytene chromosome preparations. At the top, the recruitment of the GAL4 DNA-binding region alone (DBD) did not induce the formation of the interband in the 10A1-2 band (negative control). At the bottom, the recruitment of the GAL4 DNA-binding region fused with 1–1096 aa CP190 induces the formation of the interband in the 10A1-2 band (positive control). Scale bars, 10 μm. (B) Summary of the results for attracting truncated versions of CP190 to 16xGAL4 binding sites in the 10A1-2 band. The truncated versions of CP190 were fused with the GAL4 DNA-binding region: DBD:CP190(1–309), DBD:CP190(1–430), DBD:CP190(1–470), DBD:CP190(1–590), and DBD:CP190(1–755). “Interband” represents the presence (“yes”) or absence (“no”) of the interband in the 10A1-2 band model system. The results of CP190, Z4, and Chriz protein recruitment are summarized in columns with “++”, “+” and “−” signs referring to the full, partial presence, or absence, respectively, of tested proteins in the generated interband in the 10A1-2 band. Other terms are as in Figure 1.