The function of ENSG00000165030 (NFIL3, nuclear factor, interleukin 3 regulated) is as follows. 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 (By similarity). Represses the transcription of CYP2A5 (By similarity). Positively regulates the expression and activity of CES2 by antagonizing the repressive action of NR1D1 on CES2 (By similarity). Required for the development of natural killer cell precursors (By similarity). {ECO:0000250|UniProtKB:O08750, ECO:0000269|PubMed:1620116, ECO:0000269|PubMed:7565758, ECO:0000269|PubMed:8836190}.