Fig. 3. mSin3 interacts with RD-2b of TGIF. A, COS-1 cells were transfected with the indicated Flag-tagged TGIF expression constructs, together with myc-Sin3. Proteins were precipitated on Flag-agarose and analyzed for the presence of myc-Sin3 (arrow). Expression levels of transfected proteins were assessed by Western blotting a portion of the lysate (below). B, COS-1 cells were transfected and analyzed as in A, except that TGIF was tagged with two HA epitopes, and proteins were precipitated using an HA-specific antibody. C, the TGIF deletion constructs used in A and B are shown schematically. Diagonal stripes, RD-2a, and RD-2b. Vertical stripes within RD-1, the CtBP-interaction motif. The positions of the Flag (FL) and HA epitopes are shown. The interaction of each construct with mSin3 (from A and B) is shown. +++, strong interaction; ++, slight decrease in the interaction; +, barely detectable interaction; -, no detectable interaction.