RNA-independent interaction between Paip1 and eIF3. (A) GST pull-down experiments were conducted with GST-Paip1 or GST on HeLa cell extracts. Eluates were subjected to SDS-PAGE. Bands unique to GST-Paip1 (circled) were excised and subjected to mass spectrometry analysis. Identified proteins are indicated next to the analyzed bands. Protein sequence coverage is as follows: eIF3a, 15.4%; eIF3b, 14.4%; eIF3c, 20.2%; PABP, 56.0%; eIF3g, -h, and -i, ∼10%. (B) GST pull-downs were conducted with GST-Paip1 or GST in untreated or micrococcal nuclease-treated HeLa cell extracts. Eluates were subjected to SDS-PAGE and Western blotting (WB) using the indicated antibodies. (C) Immunoprecipitation using anti-eIF3 antibody (eIF3) or preimmune goat serum (IgG) was conducted using a HeLa cell extract. Extract (Input) and eluates (IP) were subjected to SDS-PAGE and Western blotting using the indicated antibodies. The Paip1 isoforms and IgG heavy chain (HC) are indicated. (D) GST pull-downs were conducted with GST or GST-Paip1 together with purified eIF3. Eluates were subjected to SDS-PAGE and Western blotting using the indicated antibodies.