The HOXA11 protein is a transcription factor encoded by the HOXA11 gene, a member of the HOXA gene cluster in the homeobox gene family.The core structure of HOXA11 protein is the homologous domain, which is composed of about 60 amino acids. HOXA11 plays an integral role in the normal development of the urogenital system and precisely regulates the morphogenesis of the forearm and wrist during limb development.In addition, it is involved in the regulation of cell differentiation, proliferation and apoptosis.Forkhead Box Protein O1 (FOXO1) has been identified as an interactor of HOXA11, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human HOXA11 and recombinant mouse FOXO1. Briefly, biotin-linked HOXA11 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to FOXO1-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50µl stop solution to the wells and read at 450nm immediately. The binding activity of HOXA11 and FOXO1 was shown in Figure 1, the EC50 for this effect is 4.85ug/mL.