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 (PubMed:29061846). Can also inhibit the histone methyl-binding abilities of SPIN2A, SPIN2B, SPIN3 and SPIN4 (By similarity). Interacts with SPIN1, SPIN2A, SPIN2B, SPIN3 and SPIN4. Interacts with TCF7L2 in a SPIN1-dependent manner.