Class E basic helix-loop-helix protein 41 (Bhlhb3)

Transcriptional repressor involved in the regulation of the circadian rhythm by negatively regulating the activity of the clock genes and clock-controlled genes. Acts as the negative limb of a novel autoregulatory feedback loop (DEC loop) which differs from the one shaped by the PER and CRY transcriptional repressors (PER/CRY loop).

These two loops are interlocked as it represses the expression of PER1 and in turn is repressed by PER1/2 and CRY1/2. Represses the activity of the circadian transcriptional activator: CLOCK-ARNTL/BMAL1 heterodimer by competing for the binding to E-box components (5'-CACGTG-3') found inside the promoters of its target genes.