Transcription of eukaryotic protein-coding genes requires RNA polymerase II (Pol II). During transcription, RNA polymerase II transcribes a chromatinized DNA template. Pol II passage, however, is impaired by nucleosomes and requires elongation factors including chromatin remodelers and histone chaperones that facilitate chromatin transcription. To understand the mechanistic basis of nucleosome passage, we have obtained multiple cryo-electron microscopy structures of transcribing RNA polymerase II engaged with a downstream nucleosome core particle and additional factors. The structures and additional biochemical data provide a structural basis to investigate the interplay of Pol II, transcription factors, chromatin remodelers, histone chaperones, and nucleosomes.
