This transcriptional activator recognizes and binds to the sequence 5'-RTTAYGTAAY-3' found in the promoter of genes such as albumin, CYP2A4 and CYP2A5. It is not essential for circadian rhythm generation, but modulates important clock output genes. May be a direct target for regulation by the circadian pacemaker component clock. May affect circadian period and sleep regulation (By similarity). Binds DNA as a homodimer or a heterodimer. Can form a heterodimer with TEF (By similarity). Belongs to the bZIP family. PAR subfamily.