Common Themes in Assembly and Function of Eukaryotic Transcription Complexes

Eukaryotes contain three distinct RNA polymerase enzymes, each responsible for the transcription of a subclass of nuclear genes. Despite this division of labor, each RNA polymerase system follows a common blueprint to execute the loading of the polymerase onto the relevant promoter region. The RNA polymerase II system appears unique in that after RNA polymerase II has loaded onto the DNA, two auxiliary factors, TFIIE and TFIIH, are necessary for its escape from the promoter region. The complexity of the RNA polymerase II initiation pathway provides a multitude of potential targets for transcriptional activators. Tight control over transcription initiation levels is afforded by multiple cofactors that both enhance and repress.