From carpet bombing to cruise missiles: the 'second-order' mechanisms used by transcription factors to ensure specific DNA binding in vivo.

Transcription factors generally have only modest specificity for their target sites, yet must find them in a sea of non-specific DNA. Some transcription factors are expressed at very high levels, to ensure that, despite losses to non-specific binding, the promoter is still occupied (the carpet-bombing strategy). Others increase their binding specificity by collaborating with other factors in a variety of ways.