Fig. 3. Nuclear localization of rp3, facilitated by its interaction with the N-terminal region of SATB1. (A) Schematic diagram of SATB1 and the expression constructs of SATB1 used for transfection (top). Boxes label the PDZ domain, the MAR binding domain and the atypical homeodomain (HOX) motif. Immunolabeling of Flag-tagged SATB1, SATB1-N and SATB1-C in transfected HEK cells (bottom). (B) HEK cells co-transfected with rp3 and various Flag-SATB1 constructs were immunoprecipitated with anti-Flag antibody followed by immunoblotting for either Flag or rp3. The immunoblots of total inputs are also shown. (C) Colocalization study of HEKs singly transfected with GFP-rp3, or double transfected with GFP-rp3 or GFP-IC, together with various Flag-SATB1 constructs for GFP (green) and Flag (red). (D) Nuclear Flag-SATB1 (red) and GFP-rp3 (green) were co-distributed in the interchromatin spaces surrounding heterochromatin, the dense regions of DAPI staining, in transfected cells (top panel). Nuclear colocalized Flag-SATB1 and GFP-rp3 remained in the nuclear matrix after DNaseI digestion (bottom panel). Bar, 5 µm.