Specific transcription factors (sTFs) are proteins binding to DNA, allowing control of a gene’s or group of genes’ transcriptional activity. Multiple sTFs can bind to regulatory DNA regions, to allow control of gene expression through a range of values, instead of as an ‘on/off’ switch. Although transcription factors can bind to any regulatory element to upregulate the expression of a gene, promoter-proximal elements (PPEs) are one site they do bind to. These are regulatory sites around 200 base pairs upstream of the transcriptional start site, and different PPEs can be combined to allow different transcription factors to exert an effect on one gene.
The same transcription factor can increase the expression of multiple genes, where the same protein binding site is present in the DNA. This allows the formation of regulons in eukaryotes - these are functionally linked genes that can be controlled through the same mechanism. This allows the expression of a group of genes to be induced by a single transcription factor. In metabolic pathways, where several enzymes may be required to produce the final product, they could be grouped together into a regulon. This would allow a single transcription factor to allow the expression of the group of genes, enabling coordinated expression. This is beneficial, as it reduces the complexity of metabolic pathways, ensuring that all of the components are present to allow the pathway to complete producing a final product.