SNAP output for PDB entry 7nkx [SNAP web server]

PDB-id

7nkx; SNAP-derived features in text and JSON formats; DNAproDB

Class

transcription

Method

cryo-EM (2.9 Å)

Summary

RNA polymerase ii-spt4-5-nucleosome-chd1 structure

Reference

Farnung L, Ochmann M, Engeholm M, Cramer P (2021): "Structural basis of nucleosome transcription mediated by Chd1 and FACT." Nat.Struct.Mol.Biol., 28, 382-387. doi: 10.1038/s41594-021-00578-6.

Abstract

Efficient transcription of RNA polymerase II (Pol II) through nucleosomes requires the help of various factors. Here we show biochemically that Pol II transcription through a nucleosome is facilitated by the chromatin remodeler Chd1 and the histone chaperone FACT when the elongation factors Spt4/5 and TFIIS are present. We report cryo-EM structures of transcribing Saccharomyces cerevisiae Pol II-Spt4/5-nucleosome complexes with bound Chd1 or FACT. In the first structure, Pol II transcription exposes the proximal histone H2A-H2B dimer that is bound by Spt5. Pol II has also released the inhibitory DNA-binding region of Chd1 that is poised to pump DNA toward Pol II. In the second structure, Pol II has generated a partially unraveled nucleosome that binds FACT, which excludes Chd1 and Spt5. These results suggest that Pol II progression through a nucleosome activates Chd1, enables FACT binding and eventually triggers transfer of FACT together with histones to upstream DNA.