(A) Schematic representation of Stau1, showing its dRBDs I–IV (boxes) and PP1 interaction domain (circle), as well as different GST fusion proteins. Table 1 summarizes whether the corresponding GST fusion proteins are able to pull-down rat brain P0, PP1 and PABP. (B) Western blots of GST pull-down experiments probed with specific antibodies against P0, PABP, PP1α and EF1α. Pull-downs were performed with the indicated GST fusion proteins and an adult rat brain lysate. P0 and PABP are only pulled-down by fusion proteins containing dsRBD III. PP1 precipitation requires the previously characterized PP1 interaction site. (C) Western blots of anti-FLAG immunoprecipitates obtained from HEK-293 cells co-expressing full-length or truncated versions of EGFP-tagged P0, together with either FLAG–Stau1 (upper row) or FLAG–hnRNPK (lower row). Recombinant proteins were detected with either anti-FLAG or anti-GFP antibodies. P0 co-immunoprecipitates with recombinant Stau1, but not with hnRNPK. I, input; S, supernatant fraction; P, pellet fraction.