Acts both as a transcriptional activator and a repressor (PubMed:10359848, PubMed:29739711). Binds to the DNA sequence 5'-ACAAT- 3' and shows a preference for guanine residues surrounding this core motif (PubMed:10359848). Binds to its own promoter and activates its own transcription (By similarity). Required to activate the expression of postmeiotic genes involved in spermiogenesis (By similarity). Binds to the promoter region of CTNNB1 and represses its transcription which leads to inhibition of Wnt signaling (PubMed:29739711). Also inhibits Wnt signaling by binding to the CTNNB1 protein, preventing interaction of CTNNB1 with TCF7L2/TCF4 (PubMed:29739711). {ECO:0000250|UniProtKB:Q8CGW4, ECO:0000269|PubMed:10359848, ECO:0000269|PubMed:29739711}. This is the function of ENSG00000039600 (SOX30, SRY-box transcription factor 30).