In vitro protein binding experiments have shown that mammalian SOX4, SOX13 and SOX17 can directly interact with TCF (T-cell factor) (Sinner at al. 2007). SOX4 and SOX17 can interact with either TCF or beta-catenin protein. They have opposite effects on Wnt signalling, SOX4 enhances while SOX17 represses Wnt activity (Sinner et al. 2007). SOX13 is known to repress Wnt signaling by interacting and sequestering TCF1 from the Wnt transcriptionally active complex (Melichar et al. 2007). SOX and TCF proteins interact with overlapping armadillo repeats with in beta-catenin and thus might compete for beta-catenin binding (Kormish et al. 2010).