Transcriptional regulator which can act as an activator or a repressor. Inhibits the enhancer element of the AFP gene by binding to its AT-rich core sequence. In concert with SMAD-dependent TGF-beta signaling can repress the transcription of AFP via its interaction with SMAD2/3 (PubMed:25105025). Regulates the circadian locomotor rhythms via transcriptional activation of neuropeptidergic genes which are essential for intercellular synchrony and rhythm amplitude in the suprachiasmatic nucleus (SCN) of the brain (By similarity). Regulator of myoblasts differentiation through the binding to the AT-rich sequence of MYF6 promoter and promoter repression (PubMed:11312261). Down-regulates the MUC5AC promoter in gastric cancer (PubMed:17330845). In association with RUNX3, up-regulates CDKN1A promoter activity following TGF-beta stimulation (PubMed:20599712). Inhibits estrogen receptor (ESR1) function by selectively competing with coactivator NCOA3 for binding to ESR1 in ESR1-positive breast cancer cells (PubMed:20720010). {ECO:0000250|UniProtKB:Q61329, ECO:0000269|PubMed:11312261, ECO:0000269|PubMed:17330845, ECO:0000269|PubMed:20599712, ECO:0000269|PubMed:20720010, ECO:0000269|PubMed:25105025}. This is the function of Ensembl gene identifier ENSG00000140836 (ZFHX3, zinc finger homeobox 3).