CaAT

CAAT is most commonly associated with a promoter element in eukaryotic genes known as the CAAT box. The CAAT box is a short DNA sequence, typically with the consensus motif CCAAT, located about 75 to 80 bases upstream of the transcription start site. It often coexists with other core promoter elements, such as the TATA box, and contributes to the regulation of transcription by influencing promoter strength and chromatin accessibility. The CAAT box is enriched in promoters of many housekeeping genes and a subset of developmentally regulated genes.

A key mechanism for CAAT box activity involves transcription factors that recognize the motif. Nuclear factor Y (NF-Y), a trimetric complex composed of NF-YA, NF-YB, and NF-YC subunits, is a well-established CAAT box–binding factor in many species. Binding of NF-Y to the CAAT box can help recruit the transcriptional machinery and modulate chromatin structure, thereby enhancing transcription. Other CAAT-related binding proteins include members of the CAAT/enhancer-binding protein (C/EBP) family, which can recognize CAAT-containing contexts and regulate gene expression in tissue- and signal-specific ways. C/EBP proteins are basic leucine zipper (bZIP) transcription factors that may act as activators or repressors depending on context and dimerization partners.

Beyond the promoter motif, CAAT as an acronym may appear in other, less common contexts; however, in genetics and molecular biology, the CAAT box is the most widely encountered usage. When encountered, its exact role is inferred from the promoter context and the transcription factors present.