Structure of a backtracked hexasomal intermediate of nucleosome transcription

During gene transcription, RNA polymerase II (RNA Pol II) passes nucleosomes with the help of various elon-gation factors. Here, we show that RNA Pol II achieves efficient nucleosome passage when the human elon-gation factors DSIF, PAF1 complex (PAF), RTF1, SPT6, and TFIIS are present. The cryo-EM structure of an intermediate of the nucleosome passage shows a partially unraveled hexasome that lacks the proximal H2A-H2B dimer and interacts with the RNA Pol II jaw, DSIF, and the CTR9trestle helix. RNA Pol II adopts a backtracked state with the RNA 3' end dislodged from the active site and bound in the RNA Pol II pore. Addi-tional structures and biochemical data show that human TFIIS enters the RNA Pol II pore and stimulates the cleavage of the backtracked RNA and nucleosome passage.

Automated summary

During gene transcription, the presence of human elongation factors DSIF, PAF1 complex (PAF), RTF1, SPT6, and TFIIS facilitates efficient nucleosome passage by RNA polymerase II.