Negatively regulates the transcriptional activator activity of SPIN1 via inhibition of its histone methyl-binding ability. Represses the expression of a number of SPIN1-regulated genes and the SPIN1-mediated activation of the Wnt signaling pathway. Can also inhibit the histone methyl-binding abilities of SPIN2A, SPIN2B, SPIN3 and SPIN4 (PubMed:29061846). Interacts with SPIN1, SPIN2A, SPIN2B, SPIN3 and SPIN4 (PubMed:29061846). Interacts with TCF7L2 in a SPIN1-dependent manner (PubMed:29061846).