Getting up to speed with transcription elongation by RNA polymerase II

RNA polymerase II (Pol II) elongation is a highly regulated process.Regulation of transcription is often mediated at the level of promoter-proximal pausing of Pol II, in which Pol II is paused approximately 30–60 nucleotides downstream of the transcription start site (TSS) and awaits recruitment of kinase positive transcription elongation factor-b (P-TEFb).P-TEFb is the main factor required to release paused Pol II from the promoter-proximal region, and can directly or indirectly be recruited by many factors, including bromodomain-containing protein 4 (BRD4) and the super elongation complex (SEC).Elongation rates throughout the gene body are not uniform but vary between, and within genes, and can range from ∼1 to 6 kb per minute.Transient slowdown of Pol II is observed up to 15 kb downstream of the TSS, at exons and near the poly(A) cleavage site.Elongation rates can affect co-transcriptional RNA processes such as splicing and termination, as well as genome stability.