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A promoter site is a region of DNA that RNA polymerase binds to in order to carry out transcription. It is located upstream of the target sequence [1]. A promoter sequence determines where transcription of a gene will begin and also dictates the efficiency with which transcription takes place - cells use the degree of efficiency regulate the amount of a particular protein produced.

When analysed, the promoter regions of different genes are found to be very similar. If we compare these sequences from different genes, the most common bases for each position in the promoter region provide sequences known as 'consensus sequences'. These often determine the strength of the promoter regions. The more closely the sequence of a promoter matches the consensus sequence, the stronger it is. A weak promoter will not recruit RNA polymerase as efficiently as a strong promoter.

A common feature of promoter regions in eukaryotes is the TATA box, it is found ~10 bases upstream from the transcription start site and has the ideal sequence of TATAAAT. The closeness of the actual sequence to this ideal sequence effects the ability of the RNA polymerase complex to bind to the DNA and hence the transcription process.


  1. Biochemistry, 6th Edition, Jeremy M. Berg, John L. Tymoczko, Lubert Stryer, W. H. Freeman and Company, New York, 2008
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