Transcriptional regulator of the circadian clock components: CLOCK; ARNTL/BMAL1; ARNTL2/BMAL2; PER1/3; CRY1/2; NR1D1/2 and RORA/C. Positively regulates the transcriptional activity of CLOCK a core component of the circadian clock. Regulates transcription through chromatin remodeling by interacting with other proteins in chromatin as well as proteins in the basic transcriptional machinery. May be important for embryonic and postnatal development. May be involved in neuronal differentiation. {ECO:0000269|PubMed:22578325}.