HOXC13 protein is a transcription factor encoded by the HOXC13 gene, which is part of the HOXC gene cluster within the homeobox gene family. It contains a highly conserved homeodomain, typically composed of around 60 amino acids. This domain is responsible for making specific contacts with the major groove of the DNA double - helix. This allows the HOXC13 protein to bind to specific DNA sequences in the regulatory regions (such as promoters and enhancers) of its target genes, thereby regulating their transcriptional activity.In embryonic development, HOXC13 is crucial for the proper development of the appendages, particularly the hair, nails, and the axial skeleton.  It also plays a significant role in epithelial differentiation processes.Besides,Forkhead Box P3 (FOXP3) has been identified as an interactor of  HOXC13, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human  HOXC13 and recombinant human FOXP3 .Briefly, biotin-linked  HOXC13 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to FOXP3-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 HOXC13 and FOXP3 was shown in Figure 1, the EC50 for this effect is0.80ug/mL.