The front cover illustration shows the transcriptional regulation of the mouse D-amino acid oxidase (DAO) gene. Key TFs act on the core promoter to stimulate DAO expression, leading to D-serine metabolism and influencing neurotransmission. This reflects the study's discovery of conserved regulatory elements in DAO gene control.

D-amino acid oxidase (DAO) catalyzes oxidative deamination of D-amino acids, producing 2-oxo acids, hydrogen peroxide, and ammonia. In mammals, DAO is essential for metabolizing both endogenous and exogenous D-amino acids. Previous studies on human DAO identify two promoter regions (P1 and P2), a negative regulatory element in intron 1, and several transcription factor (TF) binding sites. In this study, the regulatory mechanism of mouse DAO gene expression is investigated to compare with the human system. To determine the promoter activity in the upstream region of the initiation site, plasmids containing mouse DAO gene fragments inserted into the pGL4 [luc2P/Hygro] vector and assessed luciferase activity in LLC-PK1 cells are constructed. A series of deletion constructs is analyzed, revealing promoter activity in all tested fragments. The highest promoter activity is detected in the −333/−87 subregion, with residual activities in the −87/ + 111 region. Bioinformatics analysis identifies TFs, including NEUR, EGRF, ZF07, ZF11, KLFS, SP1F, and ZF02, which bind to both the human and mouse DAO genes at conserved positions, suggesting their critical role in regulating DAO promoter activity.