The protein encoded by this gene is a transcriptional regulator that binds as a homodimer to activating transcription factor (ATF) sites in many cellular and viral promoters. The encoded protein represses PER1 and PER2 expression and therefore plays a role in the regulation of circadian rhythm. Three transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Feb 2014],function:Acts as a transcriptional regulator that recognizes and binds to the sequence 5′-[GA]TTA[CT]GTAA[CT]-3′, a sequence present in many cellular and viral promoters. Represses transcription from promoters with activating transcription factor (ATF) sites. Represses promoter activity in osteoblasts (By similarity). Represses transcriptional activity of PER1 (By similarity). Represses transcriptional activity of PER2 via the B-site on the promoter (By similarity). Activates transcription from the interleukin-3 promoter in T-cells. Competes for the same consensus-binding site with PAR DNA-binding factors (DBP, HLF and TEF) (By similarity). Component of the circadian clock that acts as a negative regulator for the circadian expression of PER2 oscillation in the cell-autonomous core clock (By similarity). Protects pro-B cells from programmed cell death.,induction:Up-regulated by PHA or TPA.,similarity:Belongs to the bZIP family. NFIL3 subfamily.,similarity:Contains 1 bZIP domain.,subunit:Homodimer. Binds DNA as a dimer. Interacts with DR1. Interacts with PER2 and CRY2.,tissue specificity:Expressed in bladder stomach, thyroid, spinal cord, lymph node, trachea, adrenal gland, bone marrow and muscle.,