FOXP1 physically interacts with FOXO1 in vivo and in vitro.
A, immunoblotting (IB) of HA and FLAG in FLAG immunoprecipitates (IP) from HEK293A cells expressing FLAG-tagged FOXP1 and HA-tagged FOXO1. B, immunoblotting of FOXO1 and FOXP1 in FOXO1 immunoprecipitates from liver tissue of db/db mice infected with Ad-FOXP1. C, GST pulldown experiments with anti-HA antibody as described under “Experimental Procedures” (left panel). Schematic representation of the FOXP1 protein is shown with the various functional domains indicated (right panel). GST-FOXP1 (amino acids 145–653) contains a zinc finger (amino acids 338–361), a leucine zipper (amino acids 378–403), a forkhead domain (amino acids 495–578).