In living organisms, transcription of deoxyribonucleic acid (DNA) is the initial step necessary for the expression of a gene. The TATA box, also known as the Goldberg-Hogness box, is a region of DNA that helps initiate the process of transcription. It is part of the promoter region, which regulates gene expression by providing a binding site for enzymes involved in transcribing genes. The TATA box is found in eukaryotes — organisms that have complex membrane-bound structures within their cells — including humans.
DNA consists of nucleotides, repeating structural units that come in four varieties: the nucleobases adenine (A), thymine (T), guanine (G), and cytosine (C). As these bases repeat, they form patterns that encode genetic information. They also form pairs by chemically bonding in a complementary fashion, with adenine attaching to thymine and guanine attaching to cytosine. Base pairs connect the two strands of a DNA molecule into a double helix structure.
When DNA is transcribed, enzymes split the double helix into its constituent threads, exposing the genetic code for duplication. Each DNA strand is used as a template for synthesizing a strand of ribonucleic acid (RNA). An enzyme known as RNA polymerase constructs the RNA chain by binding complementary nucleobases to each exposed DNA strand.
In order for complete genes to be transcribed into messenger RNA (mRNA) for eventual expression, RNA polymerase must begin transcription at the correct point in the DNA sequence. This point, known as the initiation site, is indicated by a promoter region that occurs slightly upstream of the gene. The TATA box is a sequence of DNA, consisting of nucleobases TATAAA, located in the promoter region about 25 base pairs before the site of transcription.
Proteins known as transcription factors bind to the TATA box. One of these, the TATA-binding protein (TBP), is TATA-specific, while the others may be able to bind to non-TATA promoter regions. RNA polymerase is able to recognize the presence of transcription factors as a signal to bind to that location. After binding to the TATA box, RNA polymerase is at the initiation site and can now begin to transcribe the gene.
Most promoter regions of genes do not contain a TATA box. In TATA-less genes, transcription factors recognize other promoter sequences and RNA polymerase binds to these instead. Researchers have discovered differences in regulation between genes with the TATA box and those without the TATA box through the study of model organisms such as Saccharomyces yeast and the fruit fly Drosophila.