FOXO3a interacts with ER-α and ER-β. (a) Total lysates of 293T cells co-transfected with hemagglutinin (HA)-tagged forkhead box class O (FOXO)3a plus Flag-estrogen receptor (ER)-α (lanes 2, 3) or an empty vector (lane 1) or an ErbB2 expression vector (lane 4), in the presence or absence of 17β-estradiol (E2), were analyzed by immunoprecipitation (IP) with an anti-HA antibody followed by immunoblotting (IB) with an anti-Flag tag antibody. (b) The same lysates of 293T cells cotransfected with HA-FOXO3a and Flag-ER-α were subjected to reciprocal IP with an anti-Flag (lane 3) or control IgG (IgG; lane 2) or anti-HA (positive control, lane 4) followed by IB with an anti-HA. (c) FOXO3a associates with ER-β. Total lysates of 293T cells co-transfected with the Flag-FOXO3a and HA-ER-β expression vectors in the presence of E2 were analyzed by the same IP/IB analysis (IP: control IgG or anti-Flag [positive control] or anti-HA [lane 3]; IB: anti-Flag). (d) The same lysates of 293T cells co-transfected with the Flag-FOXO3a and HA-ER-β expression vectors were subjected to reciprocal IP with a control IgG or anti-Flag (lane 2) or anti-HA (positive control) followed by IB with an anti-HA.