Structure of the complete elongation complex of RNA polymerase II with basal factors

In the early stage of transcription, eukaryotic RNA polymerase II (Pol II) exchanges initiation factors with elongation factors to form an elongation complex for processive transcription. Here we report the structure of the Pol II elongation complex bound with the basal elongation factors Spt4/5, Elf1, and TFIIS. Spt4/5 (the Spt4/Spt5 complex) and Elf1 modify a wide area of the Pol II surface. Elf1 bridges the Pol II central cleft, completing a "DNA entry tunnel" for downstream DNA. Spt4 and the