Cryo-EM structure of a mammalian RNA polymerase II elongation complex inhibited by alpha-amanitin.
Liu, X., Farnung, L., Wigge, C., Cramer, P.(2018) J Biol Chem 293: 7189-7194
- PubMed: 29550768
- DOI: https://doi.org/10.1074/jbc.RA118.002545
- Primary Citation of Related Structures:
6EXV - PubMed Abstract:
RNA polymerase II (Pol II) is the central enzyme that transcribes eukaryotic protein-coding genes to produce mRNA. The mushroom toxin α-amanitin binds Pol II and inhibits transcription at the step of RNA chain elongation. Pol II from yeast binds α-amanitin with micromolar affinity, whereas metazoan Pol II enzymes exhibit nanomolar affinities. Here, we present the high-resolution cryo-EM structure of α-amanitin bound to and inhibited by its natural target, the mammalian Pol II elongation complex. The structure revealed that the toxin is located in a pocket previously identified in yeast Pol II but forms additional contacts with metazoan-specific residues, which explains why its affinity to mammalian Pol II is ∼3000 times higher than for yeast Pol II. Our work provides the structural basis for the inhibition of mammalian Pol II by the natural toxin α-amanitin and highlights that cryo-EM is well suited to studying interactions of a small molecule with its macromolecular target.
Organizational Affiliation:
Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.