The key concepts of transcriptional control were established half a century ago in bacterial systems (Jacob and Monod, 1961). That pioneering work and many subsequent studies established that DNA binding transcription factors (also known as trans-factors) occupy specific DNA sequences at control elements (cis-elements) and recruit and regulate the transcription apparatus. In eukaryotic systems, there has been extensive study of specific transcription factors and their cofactors, the general transcription apparatus, and various chromatin regulators, leading to a present-day consensus model for selective gene control