CAATbox

The CAAT box is a cis-regulatory element found in the promoter regions of many eukaryotic genes. It is a short DNA motif that serves to influence transcription initiation by helping recruit the transcriptional machinery. The core consensus sequence is typically CCAAT, with common variants such as GGCCAATCT. In many genes the CAAT box is located about 75 to 80 bases upstream of the transcription start site, though its exact position can vary among promoters.

The CAAT box functions to enhance transcription efficiency and, in some promoters, is essential for robust gene expression. It often works in concert with other core promoter elements, such as the TATA box or downstream promoter elements, to modulate promoter activity. In promoters lacking a TATA box (TATA-less promoters), the CAAT box can play a particularly important role in directing transcription initiation.

The primary proteins known to bind the CAAT box are members of the NF-Y family (nuclear factor Y). NF-Y forms a trimeric complex consisting of NF-YA, NF-YB, and NF-YC subunits, which recognizes the CCAAT motif and helps recruit RNA polymerase II and other coactivators to the promoter. Additional transcription factors, including CAAT/enhancer-binding proteins (CEBPs), can interact with CAAT-related sequences in some promoters, contributing to tissue-specific or developmental regulation.

Biological significance and evolutionarily conserved nature of the CAAT box reflect its role in modulating transcription in a broad range of genes. While common, the CAAT box is not present in all promoters, and gene regulation often involves multiple elements that collectively determine expression levels.