Transcription elongation by RNA polymerase II: from regulatory complexity to disease.

Transcription elongation by RNA polymerase II (Pol II) was originally considered as the monotonic addition of ribonucleoside triphosphates to the growing nascent RNA chain. However, multiple lines of evidence now indicate that transcription elongation is a regulatory hub in gene expression that requires an increasing number of elongation factors (EFs), dysregulation of which leads to pathologies. In this review, we provide a current view of the elongation phase of Pol II, focusing on mammalian cells. We describe the increasing complexity of the mechanisms that control transcription elongation. We examine the growing set of EFs, their functional roles, and their systemic implications in human disease. Finally, we discuss the emergence of EFs as promising therapeutic targets.