Transcribing RNA polymerase III observed by electron cryomicroscopy

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• RNA polymerase (Pol) III is crucial for transcribing genes encoding essential non-coding RNAs.
• Understanding Pol III structure is key to elucidating its transcription regulation and function.

Purpose of the Study:

• To determine the high-resolution structures of RNA polymerase (Pol) III.
• To provide atomic models for functional and mechanistic studies of Pol III.

Main Methods:

• Electron cryomicroscopy (cryo-EM) was used to obtain reconstructions.
• High-resolution (3.9 Å, 4.6 Å, and 4.7 Å) structural data were achieved.
• Atomic models of Pol III were constructed based on the reconstructions.

Main Results:

• Reconstructions of elongating Pol III at 3.9 Å resolution were obtained.
• Two distinct conformations of unbound Pol III (apo Pol III) were resolved at 4.6 Å and 4.7 Å.
• Complete atomic models of Pol III were built, enabling detailed structural analysis.

Conclusions:

• The determined structures offer unprecedented atomic detail of Pol III.
• These insights facilitate understanding of Pol III's structural adaptations for its specific roles in transcription.
• The study provides a foundation for future functional and mechanistic investigations of Pol III.