Transcriptional control and transcription factors
Transcriptional control is used in both prokaryotes and eukaryotes to regulate gene expression.
Transcription is often controlled by altering the potential of RNA polymerase to bind to a promoter sequence. If it cannot bind, the gene will not be transcribed.
This modulation is mostly controlled by transcription factors. These are proteins that bind to sequences of DNA called control elements.
Transcription factors can both induce and inhibit gene expression.
These proteins are not transcription factors as they do not bind directly to the DNA.