14-3-3σ interacts primarily with the p37 isoform of AUF1. (A) Using whole-cell HeLa lysate, 14-3-3σ was immunoprecipitated (IP) with a monoclonal antibody, resolved by SDS–PAGE and detected by immunoblot with AUF1 antibody. As a control, an equal amount of lysate was subjected to IP with anti-Flag antibody. (B) Equal amounts of purified recombinant GST-14-3-3σ or GST as a control were mixed with equal amounts of purified recombinant His-tagged p37, p40, p42 or p45 AUF1 proteins, followed by recovery using GSH-Sepharose chromatography. The association of AUF1 protein isoforms with 14-3-3σ was detected by immunoblot analysis using AUF1 antibody and ECL. Typical results from at least three independent experiments are shown.