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Cryo-EM structure of a mammalian RNA polymerase II elongation complex inhibited by α-amanitin

Xiangyang Liu1, Lucas Farnung1, Christoph Wigge1

  • 1Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.

The Journal of Biological Chemistry
|March 19, 2018
PubMed

Insights

The mushroom toxin α-amanitin binds mammalian RNA polymerase II (Pol II) with high affinity, inhibiting transcription. Cryo-EM reveals specific interactions explaining this potent inhibition by the natural toxin.

Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • RNA polymerase II (Pol II) is crucial for transcribing protein-coding genes into mRNA in eukaryotes.
  • The mushroom toxin α-amanitin inhibits Pol II by binding to the elongation complex.
  • Significant differences exist in α-amanitin affinity between yeast and metazoan Pol II.

Purpose of the Study:

  • To determine the high-resolution cryo-electron microscopy (cryo-EM) structure of α-amanitin bound to the mammalian Pol II elongation complex.
  • To elucidate the structural basis for the higher affinity of α-amanitin to mammalian Pol II compared to yeast Pol II.

Main Methods:

  • High-resolution cryo-electron microscopy (cryo-EM) was employed to visualize the complex.
  • Structural analysis focused on the binding site of α-amanitin within the mammalian Pol II elongation complex.

Main Results:

  • The cryo-EM structure reveals α-amanitin binding in a pocket within the mammalian Pol II elongation complex.
  • The toxin forms additional contacts with metazoan-specific residues, accounting for its increased affinity.
  • Mammalian Pol II exhibits approximately 3000-fold higher affinity for α-amanitin than yeast Pol II.

Conclusions:

  • The study provides a detailed structural understanding of α-amanitin's inhibition of mammalian Pol II.
  • Specific interactions with metazoan residues are key to the toxin's potent binding and transcriptional inhibition.
  • Cryo-EM is a powerful technique for studying small molecule interactions with macromolecular targets like Pol II.
Keywords:
RNA polymeraseRNA polymerase IIcryo-electron microscopystructural biologytranscription

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