biostudies-literatureUnknown12(12)Maiuri PAveraged estimates of RNA polymerase II (RNAPII) elongation rates in mammalian cells have been shown to range between 1.3 and 4.3 kb min(-1). In this work, nascent RNAs from an integrated human immunodeficiency virus type 1-derived vector were detectable at the single living cell level by fluorescent RNA tagging. At steady state, a constant number of RNAs was measured corresponding to a minimal density of polymerases with negligible fluctuations over time. Recovery of fluorescence after photobleaching was complete within seconds, indicating a high rate of RNA biogenesis. The calculated transcription rate above 50 kb min(-1) points towards a wide dynamic range of RNAPII velocities in living cells.EMBO reports1280-5https://www.ebi.ac.uk/biostudies/studies/S-EPMC3245692biostudies-literatureFast transcription rates of RNA polymerase II in human cells.PMC3245692Marcello AKnezevich AMazza DMcNally JGMaiuri PDe Marco AKula AfalseFast transcription rates of RNA polymerase II in human cells.Averaged estimates of RNA polymerase II (RNAPII) elongation rates in mammalian cells have been shown to range between 1.3 and 4.3 kb min(-1). In this work, nascent RNAs from an integrated human immunodeficiency virus type 1-derived vector were detectable at the single living cell level by fluorescent RNA tagging. At steady state, a constant number of RNAs was measured corresponding to a minimal density of polymerases with negligible fluctuations over time. Recovery of fluorescence after photobleaching was complete within seconds, indicating a high rate of RNA biogenesis. The calculated transcription rate above 50 kb min(-1) points towards a wide dynamic range of RNAPII velocities in living cells.2011-01-01T00:00:00Z2011 Dec2025-04-05T00:23:43.969Z2019-03-27T00:47:20ZS-EPMC32456922201568810.1038/embor.2011.196