Figure 4. N2 is a Gro-dependent repressor motif.

(A) Schematic representation of the Sxl repression assay. In this assay, expression of Hairy under the control of the hb promoter in the anterior region of the embryo leads to repression of Sxl transcription (blue) in females (top). Repression depends on the WRPW motif of Hairy (middle), but replacement of this motif with autonomous repressor domains (RD) restores repression function (bottom). (B) Diagram of Hairy and Hairy fusion constructs tested in the Sxl assay; all fusions carry a C-terminal HA tag (see Materials and Methods). (C-K) Effects of Hairy constructs on Sxl expression in otherwise wild-type or gro mutant embryos; all images correspond to Sxl expression in female embryos. Arrowheads indicate borders of transcriptional repression. Note that Hairy^N2 does not cause complete repression of Sxl in gro^MB41 embryos (J); this may reflect a loss of function, in this genetic background, for endogenous Hairy-related factors such as Deadpan that normally contribute to Sxl repression [46].