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It is a transcription factor from the basic-helix-loop-helix (bHLH)/ PAS protein family.
It is part of the transcriptional/translational feed back loop of the circadian timing system. It forms an heterodimer with CLOCK or NPAS2 and both translocate into the nucleus.
The heterodimer binds to E-box promoter elements of target genes. It modulates the expression of the genes cry, per, dbp, ror, ppara, namt, ccg, myod, cki.
