CAAT box


A CAAT box (also CAT box or CCAAT box) is a region of nucleotides with the following consensus sequence:

5' GGCCAATCT 3'

It is found in the promoter region of many eukaryotic genes (it is not found in prokaryotes). It is part of a family of elements called the promoter-proximal elements which act in coordination with the preinitiation complex to aid RNA polymerase in initiating transcription. Specifically the CAAT box is located about 75-80 bases upstream of the transcription initiation site, and about 150 bases upstream of the TATA box. It binds transcription factors (CAAT transcription factors, or CTFs) and thereby stabilises the nearby preinitiation complex for easier binding of RNA polymerase; it is thus a key element in regulating the frequency of transcription of the gene. CAAT boxes are rarely found in genes that express proteins that exist in all cell types.