FIG. 3.

Functional analysis of S-site mutation in the 0.9-kb ac proximal promoter. (A) Transcription assays in S2 cells revealed that mutation of the ac S site (Sm) significantly increased reporter gene expression (P = 0.0008; indicated by asterisk), compared to the wild-type (WT) promoter, when Achaete and Daughterless proteins (Ac/Da) were coexpressed. (B) Bristle phenotype of the wild-type adult thorax. (C and D) Transgenic flies containing an ac transgene with the 0.9-kb S-site mutant promoter had extra dorsocentral macrochaete (arrow in panel C), and several transgenic lines of flies had clusters of extra macrochaete in the scutellum (arrows in panel D). Together, these results suggest that the ac promoter is repressed via the S site.