Nuclear protein extracts from primary MEM cells were prepared and electrophoretic mobility shift assays were performed as described69. The sequence of the oligonucleotide from the mouse Foxo1 promoter is as follows (sense strand): 5′-GATCCAGTTAAACTTAATTAGGGGTAATAAAGTGA-3′. For supershift experiments, nuclear extracts were preincubated with an ALX3 antibody (ab64985, Abcam, Cambridge, MA, USA) before the addition of the labelled probe.