Figure 4. SU(VAR)3–9 can repress transcription when tethered to a promoter.

(A) SU(VAR)3–9 represses transcription in a TSA-dependent manner. (B) An N-terminal truncation of SU(VAR)3–9 lacking the domain that interacts with JIL-1 and RPD3 can no longer repress transcription. (C) SU(VAR)3–9's transcriptional repression capacity is 2 fold reduced in a S191A mutated SU(VAR)3–9. Drosophila SL2 cells were co-transfected with expression constructs for dorsal and twist and the reporter construct pG₅DE₅-tkluc together with the indicated plasmids coding for: GAL4-DBD or GAL4 fusion proteins of SU(VAR)3–9 (and deletions/mutations thereof) and RPD3 in the presence or absence of the histone deacetylase inhibitor trichostatin A (TSA). left: luciferase assay of the activated reporter gene after transfection with the indicated plasmids. The repression capacity of GAL4-SU(VAR)3–9 was set to 100% and all other values were normalized accordingly. right: Western Blot analysis of the extracts used for the luciferase assay using an antibody specific against the GAL4-DBD [G: GAL4 DBD; R: GAL4-Rpd3; S: GAL4- SU(VAR)3–9].