FIG. 4.

The endogenous Rfx1 represses the Rfx1 promoter reporter. A. The sequence in Rfx1 targeted by pSUPER-Rfx1 (wt) was mutated so it would not be recognized. Mutated bases are in lowercase and marked with asterisks (silent). The mutations introduced no change in the protein sequence appearing at the bottom. B. Western blot of MCF-7 cells transfected with wt HARfx1 (wt; lanes 1 and 2) or with the silent mutant resistant to degradation by pSUPER-Rfx1 (silent; lanes 3 and 4) with (+) or without (−) pSUPER-Rfx1. pEGFP-C1 (Clontech) was used as internal control (lower panel). C. Luciferase activity of the Rfx1-luciferase reporter in the presence of pSUPER or pSUPER-Rfx1 and increasing amounts of pSG5-HARfx1 silent.