DNA binding proteins are central to the regulation and execution of essential cellular processes such as replication, transcription, translation and repair. Once proteins combine with DNA there can be a number of consequences. Sometimes they merely block other processes such as transcription, a classic example being the lac repressor of the bacterium Escherichia coli. In other cases they act as enzymes such as RNA polymerase, which makes RNA using DNA as a template. DNA binding proteins can also recruit other proteins to build up functional complexes, for example the transcription factor (TFII) which builds up the transcription initiation complex.

There are essentially two kinds of protein-DNA interactions: non-specific, meaning that the protein binds anywhere along the DNA and sequence specific. Histones, proteins that are important for the packaging of DNA and maintaining chromosome structure in higher, eukaryotic, organisms, are examples of proteins that bind...