The PERIOD-2 (PER2) gene is transcribed to yield mRNA and the mRNA is translated to yield PER2 protein (Shearman et al. 1997, Nakamura et al. 2008, also inferred from mouse homologs). The promoter of the PER2 gene contains an E-box which binds the BMAL1:CLOCK (ARNTL:CLOCK) heterodimer (and probably also the BMAL1:NPAS2 (ARNTL:NPAS2) heterodimer). The BMAL1:CLOCK heterodimer activates transcription of PER2.