Fig. 6. MBF1 participates in the TDF-dependent activation. (A) Colocalization of TDF and MBF1 to the transgenic reporter TDS-lacZ on the polytene chromosome. Salivary gland polytene chromosomes were prepared from a third instar larva of a sgP[Gal4]; UAS-tdf, TDS-lacZ/+; P[FLAG-MBF1]/+ line (4-6) or the same line without TDS-lacZ (1-3) and stained with anti-TDF (2 and 5) and anti-FLAG (1 and 4) antibodies. Blue signals represent DAPI staining. Panels 3 and 6 show the merged signals. The arrow marks the locus harboring the TDS-lacZ transgene. (B) MBF1 is required for full activation by TDF in vivo. Extracts were prepared from stage 16 embryos of the indicated lines and their ß-galactosidase activities were measured. Shown are average specific activities of six independent assays with standard errors.