ABSTRACT
This chapter focuses on transcriptional regulation and introduces this control with the example of a transcription factor that is bound by a small molecule, changing the protein's affinity for its binding site on the DNA. It illustrates the relationship between the genes in the single-input module, both in terms of transcriptional regulation and the metabolic pathway. Motifs that occur significantly more often in the E. coli and yeast transcriptional regulatory networks have been identified: autoregulation, the feed-forward loop, the single-input motif, multigene feed-forward loops, bi-fans, and dense overlapping regions. Two other motifs were found to be overrepresented in the E. coli and yeast transcriptional regulatory networks: the bi-fan motif and the dense overlapping region. The single-input motif has a single transcription factor that regulates the expression of many transcription units, often including its own gene. Feed-forward loops are motifs in which a gene's expression is regulated by two transcription factors, one of which is also regulated by the other.
