Fig. 4. Identification of Hrs and GRIF1 interaction domains by deletion analysis. (A) Domain structure of GRIF1 and its deletion mutants encoded by HA-tagged cDNA constructs. (B) Interaction of full-length and truncated GRIF1 proteins with Hrs. HeLa cells were co-transfected with the indicated HA- and GFP-tagged constructs. Lysates were immunoprecipitated with anti-HA antibody, followed by immunoblotting with anti-GFP and anti-HA antibodies. The asterisk indicates a non-specific band that probably represents undissociated IgG. (C) Schematic illustrating Hrs and its deletion mutants encoded by HA-tagged cDNA constructs. The following domains are indicated: VHS (Vps27p, Hrs and STAM), FYVE (Fab1b, YOTB, Vac1p and EEA1), UIM (ubiquitin-interacting motif), P (proline-rich), CC (coiled-coil), and Q/P (glutamine- and proline-rich region). (D) Interaction of full-length and truncated Hrs proteins with GRIF1. Co-immunoprecipitation experiments were performed as in B.