Insights into transcription initiation and termination from the electron microscopy structure of yeast RNA polymerase III

Mol Cell. 2007 Mar 23;25(6):813-23. doi: 10.1016/j.molcel.2007.02.016.

Abstract

RNA polymerase III (RNAPIII) synthesizes tRNA, 5S RNA, U6 snRNA, and other small RNAs. The structure of yeast RNAPIII, determined at 17 A resolution by cryo-electron microscopy and single-particle analysis, reveals a hand-like shape typical of RNA polymerases. Compared to RNAPII, RNAPIII is characterized by a bulkier stalk and by prominent features extending from the DNA binding cleft. We attribute the latter primarily to five RNAPIII-specific subunits, present as two distinct subcomplexes (C82/C34/C31 and C53/C37). Antibody labeling experiments localize the C82/C34/C31 subcomplex to the clamp side of the DNA binding cleft, consistent with its known role in transcription initiation. The C53/C37 subcomplex appears to be situated across the cleft, near the presumed location of downstream DNA, accounting for its role in transcription termination. Our structure rationalizes available mutagenesis and biochemical data and provides insights into RNAPIII-mediated transcription.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Microscopy, Electron
  • Models, Molecular
  • Protein Conformation
  • RNA Polymerase II / genetics
  • RNA Polymerase II / metabolism
  • RNA Polymerase II / ultrastructure
  • RNA Polymerase III / genetics*
  • RNA Polymerase III / metabolism
  • RNA Polymerase III / ultrastructure
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / ultrastructure
  • Transcription Initiation Site*

Substances

  • Saccharomyces cerevisiae Proteins
  • RNA Polymerase II
  • RNA Polymerase III