An acquired state: epigenetic mechanisms in transcription.

Even when we know the primary sequences and binding specificities of every transcriptional activator and repressor, our understanding of transcriptional regulation will be rudimentary. This is partly because major aspects of gene expression are governed by epigenetic mechanisms. These mechanisms may be responsible for apparently identical sequences being read by the transcriptional machinery in two different but heritable ways: active or repressed. Epigenetic transcriptional states have been encountered in a number of recent experiments.