In molecular biology, a CCAAT box (also sometimes abbreviated a CAAT box or CAT box) is a distinct pattern of nucleotides with GGCCAATCT consensus sequence that occur upstream by 75-80 bases to the initial transcription site. The CAAT box signals the binding site for the RNAtranscription factor, and is typically accompanied by a conserved consensus sequence. It is an invariant DNA sequence at about minus 70 base pairs from the origin of transcription in many eukaryoticpromoters. Genes that have this element seem to require it for the gene to be transcribed in sufficient quantities. It is frequently absent from genes that encode proteins used in virtually all cells. This box along with the GC box is known for binding general transcription factors. CAAT and GC are primarily located in the region from 100-150bp upstream from the TATA box. Both of these consensus sequences belong to the regulatory promoter. Full gene expression occurs when transcription activator proteins bind to each module within the regulatory promoter. Protein specific binding is required for the CCAAT box activation. These proteins are known as CCAAT box binding proteins/CCAAT box binding factors.
A CCAAT box is a feature frequently found before eukaryote coding regions, but is not found in prokaryotes.