[Isoform 1]: Transcription factor that is selectively and transiently expressed in cleavage-stage embryos (PubMed:28459457). Binds to double-stranded DNA elements with the consensus sequence 5'- TAATCTAATCA-3' (PubMed:28459454, PubMed:28459457, PubMed:29572508, PubMed:30315230, PubMed:30540931). Binds to chromatin containing histone H3 acetylated at 'Lys-27' (H3K27ac) and promotes deacetylation of H3K27ac. In parallel, binds to chromatin that lacks histone H3 acetylation at 'Lys-27' (H3K27ac) and recruits EP300 and CREBBP to promote acetylation of histone H3 at 'Lys-27' at new sites (PubMed:26951377). Involved in transcriptional regulation of numerous genes, primarily as transcriptional activator, but also mediates repression of a set of target genes (PubMed:17984056, PubMed:26951377, PubMed:27378237, PubMed:28459454, PubMed:28459457, PubMed:29572508, PubMed:29618456, PubMed:30540931). Promotes expression of ZSCAN4 and KDM4E, two proteins with essential roles during early embryogenesis (PubMed:26951377, PubMed:27378237, PubMed:28459457, PubMed:29618456). Promotes nuclear translocation of CTNNB1/beta-catenin and its subsequent activation of target genes (PubMed:36158201). Heterologous expression in cultured embryonic stem cells mediates transcription of HERVL retrotransposons and transcripts derived from ACRO1 and HSATII satellite repeats (PubMed:28459457). May activate expression of PITX1 (PubMed:17984056). May regulate microRNA (miRNA) expression (PubMed:24145033). Inappropriate expression can inhibit myogenesis and promote apoptosis (PubMed:26951377, PubMed:28935672, PubMed:29618456). {ECO:0000269|PubMed:17984056, ECO:0000269|PubMed:24145033, ECO:0000269|PubMed:26951377, ECO:0000269|PubMed:27378237, ECO:0000269|PubMed:28459454, ECO:0000269|PubMed:28459457, ECO:0000269|PubMed:28935672, ECO:0000269|PubMed:29572508, ECO:0000269|PubMed:29618456, ECO:0000269|PubMed:30315230, ECO:0000269|PubMed:30540931, ECO:0000269|PubMed:36158201}. [Isoform 2]: Probably inactive as a transcriptional activator, due to the absence of the C-terminal region that is important for transcriptional activation. Can inhibit transcriptional activation mediated by isoform 1. Heterologous expression of isoform 2 has no deleterious effect on cell survival. . This is the function of Ensembl gene identifier ENSG00000260596 (DUX4, double homeobox 4).