Furthermore, genes are often flanked by several binding sites for distinct transcription factors, and efficient expression of each of these genes requires the cooperative action of several different transcription factors (see, for example, hepatocyte nuclear factors).
Ademais, os xenes están a miúdo flanqueados por varios sitios de unión para diferentes factores de transcrición, e a expresión eficiente de cada un destes xenes require a acción cooperativa de varios factores de transcrición diferentes (por exemplo no caso dos factores nucleares do hepatocito).